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"THE STATE OF THE 6.8" ... JULY, 2009 (Page 6 of 8)
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Originally Posted By ZachH318:
thank you for the info that was a good read. The only thing I am a little confused about is the DMR. What makes a barrel a DMR or what are the specs of a DMR barrel? I looked a AR performance's site and checked out the 16" barrel and they say that it's a DMR and the price looks good. I want to build a 6.8 but I don't want to build a rifle and wish I did it different after its all done so I'm stuck looking at the barrels denny has and the AR performance barrels and unsure of what to do. I want tight groups for target shooting and knock down power for big game hunting with out the kick of the .308 AR I sold because I didn't like the recoil. DMR is simply a "match" chamber. It is analogous to the "Wylde" chamber in a .223. It has just enough leade to allow for less pressure with hotter loads, but snug enough to cradle the cartridge very closely to the axis of the bore, so that accuracy is enhanced. If you reload, then the DMR might get a few tenths of an inch tighter groups for you than a SPC II chamber. All in all, if you bought a barrel from Noveske, AR Performance or Denny's you would be getting exceptionally high quality, and any of them would suit your needs well. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
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Originally Posted By V00doo:
I wonder what the 6.8 vs 5.56 at 100yds or less really equate to in accuracy/wounding performance? anyone care to share the important facts about the 2 calibers in a sentance or 2 when used in CQB? I have both and am quite pleased with accuracy at 300yds and in. at over 300yds out to 500yds I can hit the target but not with the same precision. whats the deciding factor with my mp15 and m468? I dont have liveavnimals to shoot where I am stationed now...maybe soon I will. Sure: Let's get accuracy out of the way. I don't think you will get any appreciable difference in practical accuracy between the two at CQB, or even 100 yard distances. There are bullets which perform well in both calibers for me, in this regard, but other variables (versus caliber) are more important. Wounding performance? Not much of a comparison in my experience. The 6.8 beats the 5.56 hands down. It would be hard for someone to argue that a 5.56 bullet of 62 grains at 2850 FPS could wound any better than a 90 grain bullet at 2900 FPS. These are the ballistics you might see from a 14.5 inch barrel. Not sure I get this last question, but I will try to answer it. I don't know which one performs better for you at those ranges. If it is 5.56, it could be because you are using bullets with a much higher BC. That alone will affect your overall range performance. The bullet velocity is also going to affect overall range. when you say the deciding factor....not sure to what you are alluding here. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
| hi-tech-rancher thank you very much for explaining the chamber specs. I really appreciate all the work you did in this topic about the 6.8. I learned some new info about this round and you answered the questions that I have been seeking answers for. great work and thank you. |
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I just wanted to mention that for those of you wondering about ammo availability:
SSA has finally received the shipment of new powder and is catching up on loading some of the millions of projectiles upon which they've been sitting for months. The 85 grain TSX's are available right now, and the 90 grain TNT is right around the corner. From my last contact with them, I gather that they are working around the clock 
go get 'em. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
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Originally Posted By hi-tech-rancher:
I just wanted to mention that for those of you wondering about ammo availability: SSA has finally received the shipment of new powder and is catching up on loading some of the millions of projectiles upon which they've been sitting for months. The 85 grain TSX's are available right now, and the 90 grain TNT is right around the corner. From my last contact with them, I gather that they are working around the clock
go get 'em. Great news! Thanks. Sean |
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Originally Posted By hi-tech-rancher:
I just wanted to mention that for those of you wondering about ammo availability: SSA has finally received the shipment of new powder and is catching up on loading some of the millions of projectiles upon which they've been sitting for months. The 85 grain TSX's are available right now, and the 90 grain TNT is right around the corner. From my last contact with them, I gather that they are working around the clock
go get 'em. I am still waiting for the "plinking" ammo |
Beware Panopticon
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http://marylandshooter.com/ar15/junkOne.asp
(Hot link to your hearts content)
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http://marylandshooter.com/ar15/junkOne.asp
(Hot link to your hearts content)
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Originally Posted By Maryland_Shooter:
Originally Posted By hi-tech-rancher:
I just wanted to mention that for those of you wondering about ammo availability: SSA has finally received the shipment of new powder and is catching up on loading some of the millions of projectiles upon which they've been sitting for months. The 85 grain TSX's are available right now, and the 90 grain TNT is right around the corner. From my last contact with them, I gather that they are working around the clock
go get 'em. I am still waiting for the "plinking" ammo The man says Wed. We shall see. |
Ma Duce; Making big holes in assholes since 1921.
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Originally Posted By Rocketman:
Originally Posted By Maryland_Shooter:
Originally Posted By hi-tech-rancher:
I just wanted to mention that for those of you wondering about ammo availability: SSA has finally received the shipment of new powder and is catching up on loading some of the millions of projectiles upon which they've been sitting for months. The 85 grain TSX's are available right now, and the 90 grain TNT is right around the corner. From my last contact with them, I gather that they are working around the clock
go get 'em. I am still waiting for the "plinking" ammo The man says Wed. We shall see. I'm a few days late posting this, but has everyone else got their 90-grain ammo to test yet? I have a couple of boxes now, but haven't shot any of it yet. |
...But his word was in mine heart as a burning fire shut up in my bones, and I was weary with forbearing, and I could not stay...All my familiars watched for my halting...But the LORD is with me as a mighty terrible one...
Jeremiah 20 9-11
Jeremiah 20 9-11
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Originally Posted By arowneragain:
Originally Posted By Rocketman:
Originally Posted By Maryland_Shooter:
Originally Posted By hi-tech-rancher:
I just wanted to mention that for those of you wondering about ammo availability: SSA has finally received the shipment of new powder and is catching up on loading some of the millions of projectiles upon which they've been sitting for months. The 85 grain TSX's are available right now, and the 90 grain TNT is right around the corner. From my last contact with them, I gather that they are working around the clock
go get 'em. I am still waiting for the "plinking" ammo The man says Wed. We shall see. I'm a few days late posting this, but has everyone else got their 90-grain ammo to test yet? I have a couple of boxes now, but haven't shot any of it yet. Nope - is it the plinking cost advertised? |
Beware Panopticon
®¿®
http://marylandshooter.com/ar15/junkOne.asp
(Hot link to your hearts content)
®¿®
http://marylandshooter.com/ar15/junkOne.asp
(Hot link to your hearts content)
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Nope - is it the plinking cost advertised? For some reason SSA is mudding up the water here: http://www.ssarmory.com/6.8ammunitionsales.aspx On the one hand, the "90 grain OTM" was reported to be the much anticipated "plinking" round that was to sell for something under $15 a box. On the other hand, SSA is now claiming the 90 grain Speer TNT varmint round a "6.8 SPC 90 grain TNT Practice "Plinking" Round", and is selling it for a modest discount - regularly priced about the same as the pro hunters and 110g OTM. So which is it? Is the Speer round THE plinking round and if so why is it priced the standard almost $20 a box (more shipped)? If it is not the plinking round, why has the web site mislabeled it for at least a week now? |
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Originally Posted By crenca:
Nope - is it the plinking cost advertised? For some reason SSA is mudding up the water here: http://www.ssarmory.com/6.8ammunitionsales.aspx On the one hand, the "90 grain OTM" was reported to be the much anticipated "plinking" round that was to sell for something under $15 a box. On the other hand, SSA is now claiming the 90 grain Speer TNT varmint round a "6.8 SPC 90 grain TNT Practice "Plinking" Round", and is selling it for a modest discount - regularly priced about the same as the pro hunters and 110g OTM. So which is it? Is the Speer round THE plinking round and if so why is it priced the standard almost $20 a box (more shipped)? If it is not the plinking round, why has the web site mislabeled it for at least a week now? The TNT is not the new plinking round. That is the OTM that hasn't been released yet. SSA has had the TNT round for some time with the plinking description attached to it. It can be used for plinking, but it is more expensive than the new OTM on the way. Prior to that SSA had a 90 grain sierra round, but they told me they had trouble getting the bullets and switched to the TNT. The TNT has been used as the plinking round in the past by handloaders because it is available in 650 round economy size boxes at a discount. |
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- Theodore Roosevelt.
- Theodore Roosevelt.
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Originally Posted By Desert_AIP:
The TNT is not the new plinking round. That is the OTM that hasn't been released yet. SSA has had the TNT round for some time with the plinking description attached to it. It can be used for plinking, but it is more expensive thant he new OTM on the way. Prior to that SSA had a 90 grain sierra round, but they told me they had trouble getting the bullets and switched to the TNT. The TNT has been used as the plinking round in the past by handloaders because it is available in 650 round economy size boxes at a discount. Thanks for the explanation, I was confused by that as well. I check their site frequently. |
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Ok, guys, I shot the 85 TSX and 90 TNT today.
Results here: http://www.ar15.com/forums/topic.html?b=3&f=16&t=456136&page=1 
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...But his word was in mine heart as a burning fire shut up in my bones, and I was weary with forbearing, and I could not stay...All my familiars watched for my halting...But the LORD is with me as a mighty terrible one...
Jeremiah 20 9-11
Jeremiah 20 9-11
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Originally Posted By hi-tech-rancher:
One other interesting note on the cartridge's versatility. Last night, I loaded 65 subsonic 6.8 loads. these are : -SSA brass -130 grain Nosler / Combined Technology Ballistic Silvertips -COAL of 2.295" -7.2 grains of Trail Boss -No crimp this time. Plenty of friction during seating and I usually crimp everything, but there is little need for recoil protection for the bullet. -Wolf Primer Last time I shot these, I got 1.25" group at 100 yards, but that was with an eotech and 3X magnifier. this time, I will break out the Zeiss 3-12 X 56 and shoot them off the bench. I have a feeling these things will put a pigs eye out 
I know this was argued a while back but I loaded up similar 130gr CTBS 6.8 loads and shot them about two nights ago.......rifle was ported for subs or supers so it ran great..... if you look at the energy created by a 130 @ 1050 it's pretty much in line with a 9mm parabellum, which has been pretty effective on two and four legged types over the years, and the 130's will do it at 200yds instead of at the muzzle.... I am a 300 whisper fan, but from what I could tell shooting them side by side the lighter smaller bore bullet sounded quieter.....have to find a db meter.... |
" The only way I got to keep them Tigers busy is to let them shoot holes in me..."
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Originally Posted By hi-tech-rancher:
Originally Posted By Desert_AIP:
Originally Posted By Maryland_Shooter:
I bought a Cardinal, right when the bad batch went through the place. Tested with SSA higher pressure loads and it looks OK. My luck was good. Same here. I bought two and have shot combat loads and handloads through both with no pressure signs. Good shooting barrels too! It has been shown that there were very few barrels that were affected by the chrome issue. One 68Forums member bought 20 of them, IIRC, and I believe that only 2 had bores that were slightly under spec. It is pretty sad that Tim had to go out of business over this, but this is one of the known pitfalls of chrome lining. Interestingly, it seems that Nitrocarburizing and HardBlue look very promising as possible replacements for chrome lining. We are seeing signs that the nitrocarburized barrels might just allow a little more velocity, as we further test the Lothar Walther polygonal barrels. LWRC already has a good design which seems to allow for excellent pressure reduction, even with the unnecessary 1:10 twist. I wish they would make their barrels with their good rifling design and 1:11. It would be nice to see these with a 1 in 11 twist Even Ruger who is putting out a neat little compact bolt action this year in 6.8 went with the 1 in 10 |
The truth, is the truth.. even if no one believes it..
and a lie.. is a lie...even if everyone believes it
and a lie.. is a lie...even if everyone believes it
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Originally Posted By 762x40mm:
Originally Posted By hi-tech-rancher:
One other interesting note on the cartridge's versatility. Last night, I loaded 65 subsonic 6.8 loads. these are : -SSA brass -130 grain Nosler / Combined Technology Ballistic Silvertips -COAL of 2.295" -7.2 grains of Trail Boss -No crimp this time. Plenty of friction during seating and I usually crimp everything, but there is little need for recoil protection for the bullet. -Wolf Primer Last time I shot these, I got 1.25" group at 100 yards, but that was with an eotech and 3X magnifier. this time, I will break out the Zeiss 3-12 X 56 and shoot them off the bench. I have a feeling these things will put a pigs eye out
I know this was argued a while back but I loaded up similar 130gr CTBS 6.8 loads and shot them about two nights ago.......rifle was ported for subs or supers so it ran great..... if you look at the energy created by a 130 @ 1050 it's pretty much in line with a 9mm parabellum, which has been pretty effective on two and four legged types over the years, and the 130's will do it at 200yds instead of at the muzzle.... I am a 300 whisper fan, but from what I could tell shooting them side by side the lighter smaller bore bullet sounded quieter.....have to find a db meter.... OK, you got me interested again as I have all those components listed.....
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Another load from the floor of the 10th U.S. Cavalry stables
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Now that this thread has picked up again....let me ad a few good notes:
1) the Barnes 85 grain TSX kills deer just as efficiently as it does hogs. I have now shot 7 with it, and 5 were DRT, two ran about 30 yards, and were stone dead when we go to them. The bullet expands just fine even when shot through the lungs. 2) I now have developed a 150 grain sub load. It is the Sierra Game king, loaded in SSA brass. with CCI 41 primer, and OAL 2.30", with light Lee factory crimp. The first load used 7.2 grains of Trail Boss, and was accurate, but the velocity was around 850 FPS. The great news is that they were totally stable from my 1 in 9.5 twist subsonic-dedicated barrel. It is a strange bird. It has the bore lapped with Tubbs bullets and the chamber is still SAAMI, untilI get the reamer back, and I do have a Paladin gas block on it so that I can turn off the gas. Hey, 762 X 40mm, tell me a little more about your rifle, and what powder you used. Were you getting the action to cycle with your 130 BST load? When you say "...ported for both subs and supers...," what was the gas port size? I drilled mine out to .100 and use the Paladin to change from sub to super, but I still don't have it cycling with subs. Trail Boss won't cycle anything. On the "suppressed super" setting it cycles everything to 3:30 and without a hitch. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
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Originally Posted By hi-tech-rancher:
Now that this thread has picked up again....let me ad a few good notes: 1) the Barnes 85 grain TSX kills deer just as efficiently as it does hogs. I have now shot 7 with it, and 5 were DRT, two ran about 30 yards, and were stone dead when we go to them. The bullet expands just fine even when shot through the lungs. 2) I now have developed a 150 grain sub load. It is the Sierra Game king, loaded in SSA brass. with CCI 41 primer, and OAL 2.30", with light Lee factory crimp. The first load used 7.2 grains of Trail Boss, and was accurate, but the velocity was around 850 FPS. The great news is that they were totally stable from my 1 in 9.5 twist subsonic-dedicated barrel. It is a strange bird. It has the bore lapped with Tubbs bullets and the chamber is still SAAMI, untilI get the reamer back, and I do have a Paladin gas block on it so that I can turn off the gas. Hey, 762 X 40mm, tell me a little more about your rifle, and what powder you used. Were you getting the action to cycle with your 130 BST load? When you say "...ported for both subs and supers...," what was the gas port size? I drilled mine out to .100 and use the Paladin to change from sub to super, but I still don't have it cycling with subs. Trail Boss won't cycle anything. On the "suppressed super" setting it cycles everything to 3:30 and without a hitch. Do the 150gr sub loads cycle? |
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Originally Posted By hi-tech-rancher:
.....tell me a little more about your rifle, and what powder you used. Were you getting the action to cycle with your 130 BST load? When you say "...ported for both subs and supers...," what was the gas port size? I drilled mine out to .100 and use the Paladin to change from sub to super, but I still don't have it cycling with subs. Trail Boss won't cycle anything. On the "suppressed super" setting it cycles everything to 3:30 and without a hitch. yea, sorry.....I didn't mean to make it sound like it was a snap.....as simple as port size..... as I'm sure you've seen with the evolution of the SPC and similar cartridges sometimes setting up a purpose built rifle can be a compromise...give and take... I have a 300-221 that will run 125s sub-sonics also.....I haven't heard of too many of those either.....different story, takes a good bit of work..... the barrel I used is a 1:9.5 Model 1....couldn't run it too hard up top so I decided to try it in the other direction.......moved the gas block seat back to the pistol position ( 3.630" ) .....so it runs subs but you give up on the top end.....I'm using a PRI adjustable block.....port is .100 and throttle it to what I'm shooting on the top end.... one thing that I found out running the subs is that they don't seem to produce enough pressure to expand the brass to the chamber, so you get a good bit of blow-back, and lost gas pressure, back around the cartridge....don't know if you noticed this with yours or not.....so I take brass that I shot super-sonic (fire-formed to the chamber) clean it up and neck-size it only...fits snug and don't get the blow around.....but if you chamber one you're kinda committed to shooting it or do the butt bang drill......I think one of the ways the blow-around was kept in check with the whisper was to keep the chamber / brass / die dimensions tight.... burn rates, I'm using several between lil-gun and 4895.....lil-gun is my go to powder for short systems, the case is pretty empty.....as a comparison, I've been playing around with another 6.8 cartridge with close to 6gr less capacity than the SPC....with 130s it will hit 1050fps with ~12gr of 4895, the SPC case used right at 14gr.....I guess just the difference in compression... 280 to 300 ft/lbs of energy at 200 yds ain't bad, sure it's not 500.....but I remember reading somewhere that even large bore air rifles played a part in wwII.... |
" The only way I got to keep them Tigers busy is to let them shoot holes in me..."
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I have been working with several different powders, trying to get my subs to cycle. I, too, have a Model 1 "subsonic-dedicated" barrel, and I also drilled the port out to .100.
The 150 Woodleigh "weldcore" did not cycle, and I had a harder time getting it stable, that I did with the SGK. My Trail Boss load is unbelievably quiet, and I have almost no blowback, so I think my full-sized RCBS dies allow for a little less slop in the SAAMI chamber. I also tried the 135 SMK, and once I got it stable it was not that accurate, but that is not much of a surprise. That bullet is svelte, sleek and wants to go fast. The ogive sits right at the case mouth, even if seated to 2.305". I suppose it is like driving a Ferrari through a school zone. Bullets with lots of bearing surface seem to stabilize best at these velocities. I am now trying Clays, and AA #9, and will also use a light weight carrier, to get these 150's cycling. That is plenty of Mojo, when you consider my .308 sub load is 180 grains. They are really not that far apart. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
| ooops, double tap |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
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Originally Posted By mort:
Greetings, Does anyone know if go or no-go guages are made for the "6.8 SPC II" (analogous to the 5.56 NATO) and the "6.8 DMR." chambers described in the original post? Thanks, ––mort They are all the same headspace dim. small changes in diameter, taper, neck diameter and leade length and dia do not effect headspace. |
www.AR15Performance.com
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I wanted to publicly post a "hats off" to HTR and so many others for their contributions to this and other very informative threads on the 6.8.
I have been studying/reading/researching AR-platforms for about 6 months now and had initially favored going with a .308 AR platform since I'm not enamored with the 5.56 cal that I carried for much of my time in the military. Over the last couple of months though, I have gotten turned on to the 6.8 SPC round and AR platforms and have found this thread to be very enlightening and also somewhat encouraging to hear that many are of the opinion that the 6.8 is here to stay. I believe 6.8 is where I will be buying my first AR. Thank you |
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I would like to say I've been following this thread for some time now and kudo's to all that have contributed. I'm plannig a new build very soon and will surely be going with 6.8.
My one question that I have and I've looked here for the answer and have not seen it. Can anyone tell my why all barrels are carbine gas system and there are no rifle length? Would a rifle lenghth gas system like that on a 5.56 increase dwell time and poss have an impact on accuracy or is the rifle length system have no effect or a negative effect on the funtion/accuracy of this cartrige in an ar platform. Again, thanks for all the great info and hard work put in by many here in this thread! Rsgt513 |
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Originally Posted By rsgt513:
I would like to say I've been following this thread for some time now and kudo's to all that have contributed. I'm plannig a new build very soon and will surely be going with 6.8. My one question that I have and I've looked here for the answer and have not seen it. Can anyone tell my why all barrels are carbine gas system and there are no rifle length? Would a rifle lenghth gas system like that on a 5.56 increase dwell time and poss have an impact on accuracy or is the rifle length system have no effect or a negative effect on the funtion/accuracy of this cartrige in an ar platform. Again, thanks for all the great info and hard work put in by many here in this thread! Rsgt513 The 6.8 uses faster powders and the pressure dissipates quicker in the larger bore so a rifle length is not the best unless it is at least 20" and full power handloads are used. A rifle length system needs a .093 port at least to function even with hot handloads.. |
www.AR15Performance.com
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Ahhh.... thank you ar15performance! If I would have had on my reloading hat when thinking bout gas system length it might have dawned on me...lol
The more I learn about 6.8 the more I am sold on it! Now, I gotta go get a new lower and start shoppin! Thanks again guys. Rsgt513 |
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HTR thanks for all the work and posts!.
I am close to finishing assembly of my first AR. I have gone back and forth between a 6.8 DMR or .223 Wylde. Very close to going 6.8DMR The first issue I am working out is... I would like to shoot the high pressure rounds. SSA states to purchase tactical loads I must have a “Spec II Chamber, 1x10 twist, 6-groove barrel” Neither of the barrels I am considering meet the exact requirements I have narrowed the companies of the barrel I would like to purchase down to AR Performance or Titan Armory, (same barrel depending on which side of the Mississippi you live on) or purchasing a Lothar Walther in the white. Both barrel options would come with a DMR chamber and a 1:11.25 twist. Purchasing from ARP or Titan would give me a 5R rifling while the LW would give me a polygonal rifling. The plus to the ARP or Titan barrel would be it comes finished with a properly head spaced bolt; the downside is I am not sold on having a chromed lined barrel. The plus to the LW would be polygonal rifling; the downside would be having to headspace and Nitrocarburize the barrel. My limited AR shooting experience (less than one 1994-2004 legal mag) and lack of real world operating knowledge (I have been reading about AR’s for 20+ years), leads me to believe either barrel should run high pressure 6.8 rounds just fine? I have already purchase an Adams Arms adjustable gas block and am only considering a mid length barrel. Does anyone know if high pressure loads would work in a 16” DMR chamber 1:11.25 with either 5R or polygonal rifling? |
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Originally Posted By mgx:
HTR thanks for all the work and posts!. I am close to finishing assembly of my first AR. I have gone back and forth between a 6.8 DMR or .223 Wylde. Very close to going 6.8DMR The first issue I am working out is... I would like to shoot the high pressure rounds. SSA states to purchase tactical loads I must have a “Spec II Chamber, 1x10 twist, 6-groove barrel” Neither of the barrels I am considering meet the exact requirements I have narrowed the companies of the barrel I would like to purchase down to AR Performance or Titan Armory, (same barrel depending on which side of the Mississippi you live on) or purchasing a Lothar Walther in the white. Both barrel options would come with a DMR chamber and a 1:11.25 twist. Purchasing from ARP or Titan would give me a 5R rifling while the LW would give me a polygonal rifling. The plus to the ARP or Titan barrel would be it comes finished with a properly head spaced bolt; the downside is I am not sold on having a chromed lined barrel. The plus to the LW would be polygonal rifling; the downside would be having to headspace and Nitrocarburize the barrel. My limited AR shooting experience (less than one 1994-2004 legal mag) and lack of real world operating knowledge (I have been reading about AR’s for 20+ years), leads me to believe either barrel should run high pressure 6.8 rounds just fine? I have already purchase an Adams Arms adjustable gas block and am only considering a mid length barrel. Does anyone know if high pressure loads would work in a 16” DMR chamber 1:11.25 with either 5R or polygonal rifling? The 10 twist is minimum, 11 or 12 is better. The typical 6 groove has a higher land-groove ratio and will produce higher peak pressure than a barrel with a lower land-groove ratio, the number of grooves isn't really telling enough. I have seen some barrels with a 50/50 ratio, those are the ones you don't want. A barrel can be 40/60 and have 4, 5 or 6 grooves. Most specs say they must range from 40/60 - 30/70 land to groove but more and more high performance barrels with lower L-G ratios are showing up, we have 6.8 and 5.56 HP 5 groove barrels now with 30 cal and 6.5 on the way, these are not typical ratio 5R barrels. Our barrels are Nitro-carburized, I believe Art(SSA) is using our barrels/upper to send out as a loaner to SWAT teams so they can try the 6.8 ammo out. Will definitely handle SSA's combat loads. |
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Originally Posted By AR-Performance:
Originally Posted By mgx:
HTR thanks for all the work and posts!. I am close to finishing assembly of my first AR. I have gone back and forth between a 6.8 DMR or .223 Wylde. Very close to going 6.8DMR The first issue I am working out is... I would like to shoot the high pressure rounds. SSA states to purchase tactical loads I must have a “Spec II Chamber, 1x10 twist, 6-groove barrel” Neither of the barrels I am considering meet the exact requirements I have narrowed the companies of the barrel I would like to purchase down to AR Performance or Titan Armory, (same barrel depending on which side of the Mississippi you live on) or purchasing a Lothar Walther in the white. Both barrel options would come with a DMR chamber and a 1:11.25 twist. Purchasing from ARP or Titan would give me a 5R rifling while the LW would give me a polygonal rifling. The plus to the ARP or Titan barrel would be it comes finished with a properly head spaced bolt; the downside is I am not sold on having a chromed lined barrel. The plus to the LW would be polygonal rifling; the downside would be having to headspace and Nitrocarburize the barrel. My limited AR shooting experience (less than one 1994-2004 legal mag) and lack of real world operating knowledge (I have been reading about AR’s for 20+ years), leads me to believe either barrel should run high pressure 6.8 rounds just fine? I have already purchase an Adams Arms adjustable gas block and am only considering a mid length barrel. Does anyone know if high pressure loads would work in a 16” DMR chamber 1:11.25 with either 5R or polygonal rifling? The 10 twist is minimum, 11 or 12 is better. The typical 6 groove has a higher land-groove ratio and will produce higher peak pressure than a barrel with a lower land-groove ratio, the number of grooves isn't really telling enough. I have seen some barrels with a 50/50 ratio, those are the ones you don't want. A barrel can be 40/60 and have 4, 5 or 6 grooves. Most specs say they must range from 40/60 - 30/70 land to groove but more and more high performance barrels with lower L-G ratios are showing up, we have 6.8 and 5.56 HP 5 groove barrels now with 30 cal and 6.5 on the way, these are not typical ratio 5R barrels. Our barrels are Nitro-carburized, I believe Art(SSA) is using our barrels/upper to send out as a loaner to SWAT teams so they can try the 6.8 ammo out. Will definitely handle SSA's combat loads. Thanks for the clarification, are your barrels chrome lined as well as Nitro-carburized? If they are what is the advantage of having chromed lined in addition to Nitro-carburized? |
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Originally Posted By mgx:
Originally Posted By AR-Performance:
Originally Posted By mgx:
HTR thanks for all the work and posts!. I am close to finishing assembly of my first AR. I have gone back and forth between a 6.8 DMR or .223 Wylde. Very close to going 6.8DMR The first issue I am working out is... I would like to shoot the high pressure rounds. SSA states to purchase tactical loads I must have a “Spec II Chamber, 1x10 twist, 6-groove barrel” Neither of the barrels I am considering meet the exact requirements I have narrowed the companies of the barrel I would like to purchase down to AR Performance or Titan Armory, (same barrel depending on which side of the Mississippi you live on) or purchasing a Lothar Walther in the white. Both barrel options would come with a DMR chamber and a 1:11.25 twist. Purchasing from ARP or Titan would give me a 5R rifling while the LW would give me a polygonal rifling. The plus to the ARP or Titan barrel would be it comes finished with a properly head spaced bolt; the downside is I am not sold on having a chromed lined barrel. The plus to the LW would be polygonal rifling; the downside would be having to headspace and Nitrocarburize the barrel. My limited AR shooting experience (less than one 1994-2004 legal mag) and lack of real world operating knowledge (I have been reading about AR’s for 20+ years), leads me to believe either barrel should run high pressure 6.8 rounds just fine? I have already purchase an Adams Arms adjustable gas block and am only considering a mid length barrel. Does anyone know if high pressure loads would work in a 16” DMR chamber 1:11.25 with either 5R or polygonal rifling? The 10 twist is minimum, 11 or 12 is better. The typical 6 groove has a higher land-groove ratio and will produce higher peak pressure than a barrel with a lower land-groove ratio, the number of grooves isn't really telling enough. I have seen some barrels with a 50/50 ratio, those are the ones you don't want. A barrel can be 40/60 and have 4, 5 or 6 grooves. Most specs say they must range from 40/60 - 30/70 land to groove but more and more high performance barrels with lower L-G ratios are showing up, we have 6.8 and 5.56 HP 5 groove barrels now with 30 cal and 6.5 on the way, these are not typical ratio 5R barrels. Our barrels are Nitro-carburized, I believe Art(SSA) is using our barrels/upper to send out as a loaner to SWAT teams so they can try the 6.8 ammo out. Will definitely handle SSA's combat loads. Thanks for the clarification, are your barrels chrome lined as well as Nitro-carburized? If they are what is the advantage of having chromed lined in addition to Nitro-carburized? . No, just nitro-carburized. "Nitrocarburizing Nitrocarburizing is a variation of the nitriding process. It is a thermochemical diffusion process where nitrogen, carbon, and to a very small degree, oxygen atoms diffuse into the surface of the steel part, forming a compound layer at the surface, and a diffusion layer. Nitrocarburizing is a shallow case variation of the nitriding process. Advantages of the process include the ability to harden materials which are not prehardened, the relatively low temperature of the process which minimizes distortion, and relative low cost in comparison to carburizing or other case hardening processes. This process is done mainly to provide an anti-wear resistance on surface layer and to improve fatigue resistance. An additional advantage is that nitrocarburizing can be applied to the same materials as is nitriding, as well as unalloyed materials, where good wear resistance and some improved fatigue resistance are needed at a low cost. It is widely used for stampings, as an alternative to hard plating or even carbonitriding." |
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Originally Posted By AR-Performance:
Originally Posted By mgx:
HTR thanks for all the work and posts!. I am close to finishing assembly of my first AR. I have gone back and forth between a 6.8 DMR or .223 Wylde. Very close to going 6.8DMR The first issue I am working out is... I would like to shoot the high pressure rounds. SSA states to purchase tactical loads I must have a “Spec II Chamber, 1x10 twist, 6-groove barrel” Neither of the barrels I am considering meet the exact requirements I have narrowed the companies of the barrel I would like to purchase down to AR Performance or Titan Armory, (same barrel depending on which side of the Mississippi you live on) or purchasing a Lothar Walther in the white. Both barrel options would come with a DMR chamber and a 1:11.25 twist. Purchasing from ARP or Titan would give me a 5R rifling while the LW would give me a polygonal rifling. The plus to the ARP or Titan barrel would be it comes finished with a properly head spaced bolt; the downside is I am not sold on having a chromed lined barrel. The plus to the LW would be polygonal rifling; the downside would be having to headspace and Nitrocarburize the barrel. My limited AR shooting experience (less than one 1994-2004 legal mag) and lack of real world operating knowledge (I have been reading about AR’s for 20+ years), leads me to believe either barrel should run high pressure 6.8 rounds just fine? I have already purchase an Adams Arms adjustable gas block and am only considering a mid length barrel. Does anyone know if high pressure loads would work in a 16” DMR chamber 1:11.25 with either 5R or polygonal rifling? The 10 twist is minimum, 11 or 12 is better. The typical 6 groove has a higher land-groove ratio and will produce higher peak pressure than a barrel with a lower land-groove ratio, the number of grooves isn't really telling enough. I have seen some barrels with a 50/50 ratio, those are the ones you don't want. A barrel can be 40/60 and have 4, 5 or 6 grooves. Most specs say they must range from 40/60 - 30/70 land to groove but more and more high performance barrels with lower L-G ratios are showing up, we have 6.8 and 5.56 HP 5 groove barrels now with 30 cal and 6.5 on the way, these are not typical ratio 5R barrels. Our barrels are Nitro-carburized, I believe Art(SSA) is using our barrels/upper to send out as a loaner to SWAT teams so they can try the 6.8 ammo out. Will definitely handle SSA's combat loads. How are the shilen 16" 1-11 4groove Bbl ? Thinking of getting one just wanted your professional opinion. This will be my first 6.8 and want to do it right ! Iwill be building off of MEGA billet upper/ lower/ ch combo , DD lite rail , Geissele Hi Speed Trigger ,and a UBR ETA- sorry if i missed carbine or middy gas system best for 14.4 -16" Bbl? |
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I think Tim and I are the only ones using 5 grooves, our 5 groove and most 4 groove will produce lower pressures than a 6 groove.
Most 6 grooves I see are almost 50:50 land to groove ratio, made that way because barrel makers can pull the button faster because less material is displaced. A 50:50 ratio decreases bore area and raises pressures. Most specs state the L-G ratio should be 40:60 - 30:70. |
www.AR15Performance.com
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Originally Posted By AR-Performance:
I think Tim and I are the only ones using 5 grooves, our 5 groove and most 4 groove will produce lower pressures than a 6 groove. Most 6 grooves I see are almost 50:50 land to groove ratio, made that way because barrel makers can pull the button faster because less material is displaced. A 50:50 ratio decreases bore area and raises pressures. Most specs state the L-G ratio should be 40:60 - 30:70. One of my customers just broke in his new XTreme barrel today. This is the 16" length, with 11.25 inch twist and 5r rifling. The guy called me to say that the rifle "functioned flawlessly from the start to the finish..." He shot another 6.8 from another manufacturer and had short-stroking with it. He had shot one group with my 85 grain Barnes handloads that covered exactly .45" at 50 yards. Pretty good for a new rifle. The load was in SSA brass, with 30.5 grains of Reloder 7, Wolf Primer and OAL of 2.305". The guy did not chrono this load, but he said that there were no swipes or pressure signs. Thank you H!! |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
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Enjoyed the writeup HTR. It cleared up quite a few things about 6.8 for me. I also think MSAR has entered the SPC II market. Don't know their twist rate but I've got a post up in their industry forum that I'm sure will be answered soon. |
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I grade dinner picks harshly and fairly.
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Originally Posted By retgarr:
Enjoyed the writeup HTR. It cleared up quite a few things about 6.8 for me. I also think MSAR has entered the SPC II market. Don't know their twist rate but I've got a post up in their industry forum that I'm sure will be answered soon. I read over in the Bullpup section it will be 1/11. |
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Originally Posted By Taipan:
Originally Posted By retgarr:
Enjoyed the writeup HTR. It cleared up quite a few things about 6.8 for me. I also think MSAR has entered the SPC II market. Don't know their twist rate but I've got a post up in their industry forum that I'm sure will be answered soon. I read over in the Bullpup section it will be 1/11. I am not surprised to hear that. They contacted me a while back in preparation to release a 6.8. I am glad to see that they did some homework, rather than to release another SAAMI chambered 1:10 twist rifle. Things are definitely moving forward and that is a good thing. -Also, a couple of other notes: if you did have a 20" barrel, with rifle length gas, and you use a suppressor, there is usually enough back pressure to allow for cycling of light bullets, whereas these same loads might short-stroke in that same weapon. This is another excellent reason to own an adjustable gas block. Thus, if you shoot a rifle that is "properly gassed" from the factory, it will be "over-gassed" with a can that creates significant back pressure. the adjustable GB can ameliorate this with the turn of a screw, knob, etc. OTOH, if the rifle is a little short on gas, using a suppressor is highly preferable to drilling out the gas port. IMO, someday everyone should own a suppressor, and they should be sold by cabela's
-One of the newer enhancements we'll see in these rifles is adjustable GB's like the Paladin, Noveske's switch block, the JET model, and I believe ARP is also building one. -Another very positive note is that Barnes has finally committed to releasing a 100 grain TTSX, and Nosler is alredy selling the 100 grain Accubond to the public. With bullets like this coming out, the 6.8 will be performing at yet another level. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
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Originally Posted By hi-tech-rancher:
Originally Posted By Taipan:
Originally Posted By retgarr:
Enjoyed the writeup HTR. It cleared up quite a few things about 6.8 for me. I also think MSAR has entered the SPC II market. Don't know their twist rate but I've got a post up in their industry forum that I'm sure will be answered soon. I read over in the Bullpup section it will be 1/11. I am not surprised to hear that. They contacted me a while back in preparation to release a 6.8. I am glad to see that they did some homework, rather than to release another SAAMI chambered 1:10 twist rifle. Things are definitely moving forward and that is a good thing. -Also, a couple of other notes: if you did have a 20" barrel, with rifle length gas, and you use a suppressor, there is usually enough back pressure to allow for cycling of light bullets, whereas these same loads might short-stroke in that same weapon. This is another excellent reason to own an adjustable gas block. Thus, if you shoot a rifle that is "properly gassed" from the factory, it will be "over-gassed" with a can that creates significant back pressure. the adjustable GB can ameliorate this with the turn of a screw, knob, etc. OTOH, if the rifle is a little short on gas, using a suppressor is highly preferable to drilling out the gas port. IMO, someday everyone should own a suppressor, and they should be sold by cabela's
-One of the newer enhancements we'll see in these rifles is adjustable GB's like the Paladin, Noveske's switch block, the JET model, and I believe ARP is also building one. -Another very positive note is that Barnes has finally committed to releasing a 100 grain TTSX, and Nosler is alredy selling the 100 grain Accubond to the public. With bullets like this coming out, the 6.8 will be performing at yet another level. I can't state enough how much I like the 100gr Accubonds. They are "really" damn fine performing bullets... |
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Originally Posted By QuicksilverJPR:
Originally Posted By hi-tech-rancher:
Originally Posted By Taipan:
Originally Posted By retgarr:
Enjoyed the writeup HTR. It cleared up quite a few things about 6.8 for me. I also think MSAR has entered the SPC II market. Don't know their twist rate but I've got a post up in their industry forum that I'm sure will be answered soon. I read over in the Bullpup section it will be 1/11. I am not surprised to hear that. They contacted me a while back in preparation to release a 6.8. I am glad to see that they did some homework, rather than to release another SAAMI chambered 1:10 twist rifle. Things are definitely moving forward and that is a good thing. -Also, a couple of other notes: if you did have a 20" barrel, with rifle length gas, and you use a suppressor, there is usually enough back pressure to allow for cycling of light bullets, whereas these same loads might short-stroke in that same weapon. This is another excellent reason to own an adjustable gas block. Thus, if you shoot a rifle that is "properly gassed" from the factory, it will be "over-gassed" with a can that creates significant back pressure. the adjustable GB can ameliorate this with the turn of a screw, knob, etc. OTOH, if the rifle is a little short on gas, using a suppressor is highly preferable to drilling out the gas port. IMO, someday everyone should own a suppressor, and they should be sold by cabela's
-One of the newer enhancements we'll see in these rifles is adjustable GB's like the Paladin, Noveske's switch block, the JET model, and I believe ARP is also building one. -Another very positive note is that Barnes has finally committed to releasing a 100 grain TTSX, and Nosler is alredy selling the 100 grain Accubond to the public. With bullets like this coming out, the 6.8 will be performing at yet another level. I can't state enough how much I like the 100gr Accubonds. They are "really" damn fine performing bullets... I agree completely. I have 200 of the Noslers on order from Midway, right now. I can't wait to get them and load them over some Re 10X, to see if I can hit 3000 FPS out of my ARP barrels. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
|
Originally Posted By hi-tech-rancher:
I agree completely. I have 200 of the Noslers on order from Midway, right now. I can't wait to get them and load them over some Re 10X, to see if I can hit 3000 FPS out of my ARP barrels. Compared to the 110gr. Accubonds, how do they compare regarding retained energy at longer distances (200+yds)? I'm using a 18" CA barrel (correct specs) right now, and am looking to handload. If the velocity difference can overcome the reduced weight in regards to retained energy, I may have to give some of them a try. But then, those 100gr. TTSX sure are tempting... |
Tempus fugit. Frater, memento mori.
This saying is trustworthy and deserves full acceptance: Christ Jesus came into the world to save sinners. Of these I am the foremost. ~ 1 Tim. 1:15
This saying is trustworthy and deserves full acceptance: Christ Jesus came into the world to save sinners. Of these I am the foremost. ~ 1 Tim. 1:15
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Originally Posted By loonybin:
Originally Posted By hi-tech-rancher:
I agree completely. I have 200 of the Noslers on order from Midway, right now. I can't wait to get them and load them over some Re 10X, to see if I can hit 3000 FPS out of my ARP barrels. Compared to the 110gr. Accubonds, how do they compare regarding retained energy at longer distances (200+yds)? I'm using a 18" CA barrel (correct specs) right now, and am looking to handload. If the velocity difference can overcome the reduced weight in regards to retained energy, I may have to give some of them a try. But then, those 100gr. TTSX sure are tempting... IMO the extra velocity possible will leave the 100 with better performance at range. 3000fps should be possible with your 18" barrel, I have hit it with 16" |
www.AR15Performance.com
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Can the chrome lined barrels be reamed to the new Spc 2 chamber. I see the Ko-Tonics can not but what about the CMMG or the Double Star ? My accuracy is great is it going to go to crap when I have it changed to the Spc 2 chamber ? I load my ammo to 2.295 as it is right now but I only get about 2600 at best with a 110 Sierra Pro Hunter out of a 16 inch gun,
Thanks,Keith |
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Originally Posted By kidcoltoutlaw:
Can the chrome lined barrels be reamed to the new Spc 2 chamber. I see the Ko-Tonics can not but what about the CMMG or the Double Star ? My accuracy is great is it going to go to crap when I have it changed to the Spc 2 chamber ? I load my ammo to 2.295 as it is right now but I only get about 2600 at best with a 110 Sierra Pro Hunter out of a 16 inch gun, Thanks,Keith One of the reasons chamber reaming is so popular is that it is very easy. Any guy can do it with a few turns of the reamer. There is very little material removed, and it is exceptionally unlikely that accuracy will change at all. I have reamed out both stainless and CL'ed barrels, and never saw any accuracy change with either of them. I was able to get more powder in the loads that I ran in them. I even ran the reamer through a couple of Ko-Tonics SPCII barrels, and surprisingly enough, some material was removed. Be sure to do these things: 1) go to 68forums and get on the reamer list 2) lube the reamer and chamber during, then clean the chamber and barrel extremely well after ther procedure is done. 3) consider shooting some tubbs final finish rounds through the barrel after treatment. This will polish the throat. |
"Texas - the only state that ever kicked another country's ass."
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
"I'll never forget September 11, 2001, those who have fought and died, or those who continue to fight to avenge the deaths of over 3000 innocent Americans"
|
Originally Posted By AR-Performance:
Originally Posted By loonybin:
Originally Posted By hi-tech-rancher:
I agree completely. I have 200 of the Noslers on order from Midway, right now. I can't wait to get them and load them over some Re 10X, to see if I can hit 3000 FPS out of my ARP barrels. Compared to the 110gr. Accubonds, how do they compare regarding retained energy at longer distances (200+yds)? I'm using a 18" CA barrel (correct specs) right now, and am looking to handload. If the velocity difference can overcome the reduced weight in regards to retained energy, I may have to give some of them a try. But then, those 100gr. TTSX sure are tempting... IMO the extra velocity possible will leave the 100 with better performance at range. 3000fps should be possible with your 18" barrel, I have hit it with 16" Considering the size of the exit hole the 110gr Accubonds make traveling at around 2600fps, the 100gr at 3000 ought to be downright devastating! 
Mods, if the pic is not welcome, just delete it or PM me, and I'll delete it. |
Tempus fugit. Frater, memento mori.
This saying is trustworthy and deserves full acceptance: Christ Jesus came into the world to save sinners. Of these I am the foremost. ~ 1 Tim. 1:15
This saying is trustworthy and deserves full acceptance: Christ Jesus came into the world to save sinners. Of these I am the foremost. ~ 1 Tim. 1:15
"THE STATE OF THE 6.8" ... JULY, 2009 (Page 6 of 8)
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