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Posted: 12/16/2011 11:53:04 AM EDT
I keep running into these threads where guys say it makes no difference if you support by the barrel or by the handguard or mag etc...
So I did a quick test to show the change in impact when using the barrel for support. I am sure something like this has been posted before, but it was my excuse to do some shooting. 
Test was with 16" rifle gas barrel with M&I 15" Tube on a RRA upper. 5 shots per position w/ Black Hills 77gr. @ 50 yards. I hope someone can pull some good out of this. 
Here is the same test with a SW M&P Eotech, KAC quad, and M855 All @ 50yds w/ a 300m zero Video of SW test w. KAC quad. Both rifles were zeroed off the mag for support.
RRA Upper with YHM FF Quad Rail, Eotech, M855
Latest test: RRA NM A2, Using Iron sights, shot off the mag, sling, and barrel. Using Nosler 77gr reloads. All are 5 shots @ 50yds again. The last few test have been hampered by the limitations of the ammo and gun and optics. This latest test is w/ (IMO) the most accurate A2 out there, and good ammo & Sights. Enjoy
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Posted: 12/16/2011 12:22:57 PM EDT
[#1]
That is the reason I switched from MOE handguards to a free float tube.
I zeroed from the bench at 50 yards, shooting quarter sized groups. Buddy used the bench, I went prone to shoot the 100 yard targets. I was 6" high. |
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Posted: 12/16/2011 12:38:42 PM EDT
[#2]
your barrel support is absolute worst case scenario, and I have never seen anyone shoot that way except in your video.
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Posted: 12/16/2011 12:40:54 PM EDT
[#3]
No surprise at all, especially resting the muzzle device on a hard surface. Probably any fud could have told you that would move the POI. With a float tube the other changes are probably related to changes in how the recoil is transmitted to your shoulder more than to changes in barrel harmonics. You should have tried braced kneeling and sitting, too, just for fun. I often see 1" change in POI at 100 yards going from putting my hand palm up over a solid object and setting the handguard on it to sitting or braced kneeling. That is with a plastic handguard, and not using a shooting sling.
An interesting test would be to use a sandbagged rest and shoot groups at 100, 200, and 300 yeards while moving the rest point on the handguard from the muzzle end to the breech end. It would also be fun to try that with several "identical" rifles with identical ammo and see how much variation there is. Then throw in some tests with several identical rifles and run the same test with several different kinds of ammo to see how differently each rifle acts with each ammo. Then do it all again after swapping the float tubes to different types, and also run some with non-FF tubes. Maybe I could get a government grant so I could afford a dozen rifles and 10,000 rounds of ammo to run a more thorough test. Practically speaking, however, the only one of those groups that would make any difference in the real world is the one where you rested the muzzle device on the plastic case. I like seeing someone decide to not listen to what "everyone" knows and check it out for himself. |
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Posted: 12/16/2011 12:53:27 PM EDT
[#4]
Nice Video, would not have thought it would have been such an extreme difference.
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Posted: 12/16/2011 12:54:49 PM EDT
[#5]
I think it would be interesting to see the same test with a non free float handguard as well
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Posted: 12/16/2011 12:57:14 PM EDT
[#6]
It surprised me how much the poi shifted with the bbl supported.
I knew the poi would change, but DAMN! Thanks for posting this! |
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Posted: 12/16/2011 1:00:34 PM EDT
[#7]
Quoted:
I think it would be interesting to see the same test with a non free float handguard as well +1 |
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Posted: 12/16/2011 1:01:02 PM EDT
[#8]
Quoted:
It surprised me how much the poi shifted with the bbl supported. I knew the poi would change, but DAMN! Thanks for posting this! I agree that was dramatic - and that's just at 50 yards. |
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Posted: 12/16/2011 1:06:14 PM EDT
[#9]
Anything that comes into contact w/ the barrel will affect the barrel harmonics. Although in your case I think the result is exaggerated because of the fact that the handguard is long forcing you to rest the barrel on the brake and the blast skewed the result. If you could repeat the test using a half inch piece of plywood to support the barrel , leaving the brake free, you would have a different result. Still interesting
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Posted: 12/16/2011 1:19:51 PM EDT
[#10]
thanks for this write up. and yes it does make a difference as you've proven.
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Posted: 12/16/2011 1:35:38 PM EDT
[#11]
Quoted:
Anything that comes into contact w/ the barrel will affect the barrel harmonics. Although in your case I think the result is exaggerated because of the fact that the handguard is long forcing you to rest the barrel on the brake and the blast skewed the result. If you could repeat the test using a half inch piece of plywood to support the barrel , leaving the brake free, you would have a different result. Still interesting This sounds good. All I had was the Sius Bullet Sensor box. I thought there was wood at the range but fail. I only have that last little bit to rest on because of that tube. I will do it with my M4 next time. It will be much worse. LOL
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Posted: 12/16/2011 1:37:16 PM EDT
[#12]
Great data, thanks for doing this and posting.
Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? |
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Posted: 12/16/2011 1:59:31 PM EDT
[#13]
I'm more troubled by the difference between magazine, mid tube and unsupported points of impact than the muzzle supported. This proves that the Free float rail does not nullify the POI changes. As a #-gunner this can be detrimental considering the awkward and ever changing positions we shoot from.
I guess the next test would be to see which rail and upper receiver combos result in the least POI changes. |
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Posted: 12/16/2011 2:34:19 PM EDT
[#14]
Quoted:
Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. |
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Posted: 12/16/2011 2:52:00 PM EDT
[#15]
That is what I would expect to see. If the barrel is rested on a hard surface it will actually bounce up when fired.
The FF tube allows something to rest the weapon on or sling use without affecting the barrel. Using the mag as a rest puts a hard part of the weapon on a hard surface- again causing it to bounce. Unsupported is the least secure way to shoot so the groups will do that. When I shoot prone I use a sling to try to make the weapon set firmly against my shoulder but it still isn't a secure as using a rest or a bipod. Jim |
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Posted: 12/16/2011 3:13:16 PM EDT
[#16]
Nice rail, great test, thanks for posting.
PETE MI |
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Posted: 12/16/2011 3:25:13 PM EDT
[#17]
Quoted:
That is what I would expect to see. If the barrel is rested on a hard surface it will actually bounce up when fired. The FF tube allows something to rest the weapon on or sling use without affecting the barrel. Using the mag as a rest puts a hard part of the weapon on a hard surface- again causing it to bounce. Unsupported is the least secure way to shoot so the groups will do that. When I shoot prone I use a sling to try to make the weapon set firmly against my shoulder but it still isn't a secure as using a rest or a bipod. Jim Without a ruler for scale, I'm seeing at least a 2-3moa shift. I guess that's acceptable to some, but not to me. My goal would be a 0moa shift. |
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Posted: 12/16/2011 3:41:40 PM EDT
[#18]
Quoted:
Quoted:
That is what I would expect to see. If the barrel is rested on a hard surface it will actually bounce up when fired. The FF tube allows something to rest the weapon on or sling use without affecting the barrel. Using the mag as a rest puts a hard part of the weapon on a hard surface- again causing it to bounce. Unsupported is the least secure way to shoot so the groups will do that. When I shoot prone I use a sling to try to make the weapon set firmly against my shoulder but it still isn't a secure as using a rest or a bipod. Jim Without a ruler for scale, I'm seeing at least a 2-3moa shift. I guess that's acceptable to some, but not to me. My goal would be a 0moa shift. What would the difference be between a free float rail vs. monolithic upper? Here are some zero targets shot at 25m with a Aimpoint M4Comp. 1X magnification. This was using a Colt M4 with non-free-floating rails. I know using magnified optics would have been far more ideal, but... Prone supported. Handguards rested on sandbags. https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc7/s720x720/373916_10100966457074159_8826570_65471242_2129845607_n.jpg Prone unsupported. https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash4/s720x720/379638_10100966455746819_8826570_65471233_1592224370_n.jpg Prone supported and unsupported. Grouping centered on target is prone supported. Grouping always hits consistently to the lower right of point of aim when unsupported. https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash4/s720x720/377503_10100966456300709_8826570_65471236_1638972630_n.jpg |
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Posted: 12/16/2011 3:50:33 PM EDT
[#19]
Quoted:
Quoted:
That is what I would expect to see. If the barrel is rested on a hard surface it will actually bounce up when fired. The FF tube allows something to rest the weapon on or sling use without affecting the barrel. Using the mag as a rest puts a hard part of the weapon on a hard surface- again causing it to bounce. Unsupported is the least secure way to shoot so the groups will do that. When I shoot prone I use a sling to try to make the weapon set firmly against my shoulder but it still isn't a secure as using a rest or a bipod. Jim Without a ruler for scale, I'm seeing at least a 2-3moa shift. I guess that's acceptable to some, but not to me. My goal would be a 0moa shift. This is about right. This is why I keep a data book. If you can't take it out of the equation then you have to figure it in.
0moa shift would be nice. Hard to do on an AR platform though. I too would be curious on how a monolithic rail would compare. I will post a 16" M4 clone tomorrow with KAC rails for those asking. Thanks for looking 
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Posted: 12/16/2011 3:56:16 PM EDT
[#20]
Quoted:
Quoted:
Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 |
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Posted: 12/16/2011 4:04:03 PM EDT
[#21]
This also makes The PreditAR and OBR look more attractive. With the rail bolted to directly to the upper receiver And not contacting the barrel nut, I would imagine you would see much less deflection.
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Posted: 12/16/2011 4:11:25 PM EDT
[#22]
I would expect a monolithic upper to perform the same function as a FF tube- it prevents the barrel from contact that would interfere with harmonics or otherwise cause a change in poi.
Think about how a sling on a standard forearm affects the poi when it is pulled tight when shooting. A non free floated forearm resting on sandbags or a hard surface should cause the same difference in poi as resting the barrel on it- although it should be less of a difference. Think about using a tree limb as a rest. You rest the forearm on it- not the barrel. That is also why precision rifles mount the bipod to the forearm and have the barrels free floated. it is to isolate the barrel from contact with the stock. Jim |
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Posted: 12/16/2011 4:11:46 PM EDT
[#23]
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 It's the difference between a 2" point of contact, and a 8" point of contact. I place my entire hand under the handguard when in the prone. Now, the 6" width of the group was TOTALLY the puller of the trigger. 
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Posted: 12/16/2011 4:18:41 PM EDT
[#24]
Quoted:
No surprise at all, especially resting the muzzle device on a hard surface. Probably any fud could have told you that would move the POI. With a float tube the other changes are probably related to changes in how the recoil is transmitted to your shoulder more than to changes in barrel harmonics. You should have tried braced kneeling and sitting, too, just for fun. I often see 1" change in POI at 100 yards going from putting my hand palm up over a solid object and setting the handguard on it to sitting or braced kneeling. That is with a plastic handguard, and not using a shooting sling. An interesting test would be to use a sandbagged rest and shoot groups at 100, 200, and 300 yeards while moving the rest point on the handguard from the muzzle end to the breech end. It would also be fun to try that with several "identical" rifles with identical ammo and see how much variation there is. Then throw in some tests with several identical rifles and run the same test with several different kinds of ammo to see how differently each rifle acts with each ammo. Then do it all again after swapping the float tubes to different types, and also run some with non-FF tubes. Maybe I could get a government grant so I could afford a dozen rifles and 10,000 rounds of ammo to run a more thorough test. Practically speaking, however, the only one of those groups that would make any difference in the real world is the one where you rested the muzzle device on the plastic case. I like seeing someone decide to not listen to what "everyone" knows and check it out for himself. I see fudds resting their rifles on their barrels ALL the time. |
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Posted: 12/16/2011 4:20:11 PM EDT
[#25]
Quoted:
Quoted:
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 It's the difference between a 2" point of contact, and a 8" point of contact. I place my entire hand under the handguard when in the prone. Now, the 6" width of the group was TOTALLY the puller of the trigger. I could be wrong, but I'm assuming that the "AMU" portion of the OP's name refers to the Army Marksmanship Unit. If that's the case I would have to discount the "nut behind the trigger" as the problem. You don't make it into the AMU if you cant shoot. Hell even if you can shoot, you may not make it into the AMU. |
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Posted: 12/16/2011 5:41:09 PM EDT
[#26]
Quoted:
Quoted:
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 If that now free hand is pulling down on the upper while firing on bags you will see a big difference in groups. |
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Posted: 12/16/2011 5:51:19 PM EDT
[#27]
Quoted:
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 It's the difference between a 2" point of contact, and a 8" point of contact. I place my entire hand under the handguard when in the prone. Now, the 6" width of the group was TOTALLY the puller of the trigger. I could be wrong, but I'm assuming that the "AMU" portion of the OP's name refers to the Army Marksmanship Unit. If that's the case I would have to discount the "nut behind the trigger" as the problem. You don't make it into the AMU if you cant shoot. Hell even if you can shoot, you may not make it into the AMU. Thanks for that SGTcap 
And I assure you I was not aiming 6 inches above the target for fun. LOL With the barrel as the support it was quite steady. Its very simple, the scope always points straight like a laser and the barrel gets flexed up. I know this is old news to most here, but I just thought I would show it the best I can for the few that don't know. OBR, Preditar, AI .338 Lapua mag- would all do the same thing if you use the barrel for support. I will try and update this with a video of a more common firearm (m4 type) later.
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Posted: 12/16/2011 6:05:35 PM EDT
[#28]
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 It's the difference between a 2" point of contact, and a 8" point of contact. I place my entire hand under the handguard when in the prone. Now, the 6" width of the group was TOTALLY the puller of the trigger. I could be wrong, but I'm assuming that the "AMU" portion of the OP's name refers to the Army Marksmanship Unit. If that's the case I would have to discount the "nut behind the trigger" as the problem. You don't make it into the AMU if you cant shoot. Hell even if you can shoot, you may not make it into the AMU. Thanks for that SGTcap
And I assure you I was not aiming 6 inches above the target for fun. LOL With the barrel as the support it was quite steady. Its very simple, the scope always points straight like a laser and the barrel gets flexed up. I know this is old news to most here, but I just thought I would show it the best I can for the few that don't know. OBR, Preditar, AI .338 Lapua mag- would all do the same thing if you use the barrel for support. I will try and update this with a video of a more common firearm (m4 type) later.
If only you had a friend with an OBR that you could use to do a test with.
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Posted: 12/16/2011 6:09:54 PM EDT
[#29]
Quoted:
Thanks for that SGTcap
And I assure you I was not aiming 6 inches above the target for fun. LOL With the barrel as the support it was quite steady. Its very simple, the scope always points straight like a laser and the barrel gets flexed up. I know this is old news to most here, but I just thought I would show it the best I can for the few that don't know. OBR, Preditar, AI .338 Lapua mag- would all do the same thing if you use the barrel for support. I will try and update this with a video of a more common firearm (m4 type) later.
Like I said my concern is not the 6" change in POI due to using the barrel for support. Mine is the 2-3moa change between magazine, tube and unsupported. If I'm trying to turn a swinger at 100yds or hit a mini-popper at 2-300 that is the difference between a hit and miss. With the timer running a can barely remember one set of dope, or my stage plan, let alone multiple sets of dope. |
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Posted: 12/16/2011 6:12:06 PM EDT
[#30]
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 It's the difference between a 2" point of contact, and a 8" point of contact. I place my entire hand under the handguard when in the prone. Now, the 6" width of the group was TOTALLY the puller of the trigger. I could be wrong, but I'm assuming that the "AMU" portion of the OP's name refers to the Army Marksmanship Unit. If that's the case I would have to discount the "nut behind the trigger" as the problem. You don't make it into the AMU if you cant shoot. Hell even if you can shoot, you may not make it into the AMU. Thanks for that SGTcap
And I assure you I was not aiming 6 inches above the target for fun. LOL With the barrel as the support it was quite steady. Its very simple, the scope always points straight like a laser and the barrel gets flexed up. I know this is old news to most here, but I just thought I would show it the best I can for the few that don't know. OBR, Preditar, AI .338 Lapua mag- would all do the same thing if you use the barrel for support. I will try and update this with a video of a more common firearm (m4 type) later.
If only you had a friend with an OBR that you could use to do a test with.
Please, do this. I am curious what effect you think parallax between the various positions had on your POI. Would that account for the 2-3moa shift? |
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Posted: 12/16/2011 6:15:07 PM EDT
[#31]
Groups look good. Awesome test.
I also find it funny how he is using a $30k bullet sensor as a rest. Posted Via AR15.Com Mobile |
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Posted: 12/16/2011 6:20:53 PM EDT
[#32]
Quoted:
It surprised me how much the poi shifted with the bbl supported. I knew the poi would change, but DAMN! Thanks for posting this! It was so extreme because it was the very end he rested it on. If he rested it on the middle of the barrel it wouldnt have been nearly as much |
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Posted: 12/16/2011 6:35:07 PM EDT
[#33]
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 It's the difference between a 2" point of contact, and a 8" point of contact. I place my entire hand under the handguard when in the prone. Now, the 6" width of the group was TOTALLY the puller of the trigger. I could be wrong, but I'm assuming that the "AMU" portion of the OP's name refers to the Army Marksmanship Unit. If that's the case I would have to discount the "nut behind the trigger" as the problem. You don't make it into the AMU if you cant shoot. Hell even if you can shoot, you may not make it into the AMU. I was referring to me and my group. |
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Posted: 12/16/2011 6:35:39 PM EDT
[#34]
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Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 If that now free hand is pulling down on the upper while firing on bags you will see a big difference in groups. Explain ... 
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Posted: 12/16/2011 6:50:19 PM EDT
[#35]
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 If that now free hand is pulling down on the upper while firing on bags you will see a big difference in groups. Explain ...
If the shooter has the left hand off the rifle (right hand shooter) then there wouldn't be any difference between a sand bag or a hand under the handguard. Now if the shooter rest the free left hand on the gun or scope pulling the gun down the groups would change. At least with my rifle ..... |
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Posted: 12/16/2011 7:20:28 PM EDT
[#36]
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Great data, thanks for doing this and posting. Is there any data out there on how using a non-free-float handguard (like the MOE handguard) changes POI from shot to shot? Or even anecdotally, can I expect POI to shift around when using a hanguard supported position if it's not floated? For me, with my MOE handguards and a 50 yard zero, my rounds impacted 6" high at 100 yards just going from benched on a sandbag to prone unsupported. I started reading around, and found out that in SDM school they are taught to use the mag as a mono-pod, and place the offhand on the magwell to reduce the chance of changing barrel harmonics. No offense, but I don't see how a sandbag placed under the handguard to support the weapon is going to have any different "harmonic" effect than your palm placed under the handguard to support the weapon in a similar fashion. In this particular example, I'll suggest that the 6" difference you're seeing between those two specific shooting positions has less to do with barrel harmonics, and a whole lot more to do with the trigger puller. $.02 If that now free hand is pulling down on the upper while firing on bags you will see a big difference in groups. Explain ...
If the shooter has the left hand off the rifle (right hand shooter) then there wouldn't be any difference between a sand bag or a hand under the handguard. Now if the shooter rest the free left hand on the gun or scope pulling the gun down the groups would change. At least with my rifle ..... Agreed ... The part in blue is what I was referring to in my comments. |
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Posted: 12/17/2011 5:26:35 AM EDT
[#37]
I was at the 100 yard range one day with my 6920 that has a LaRue 7" rail on it.
I was shooting from a rest and hitting POA/POI all morning. I went to help my buddy with something on his rifle and went back to mine. Next thing I know I am shooting way high just like in the OP's pics. I did not know what the hell happened and then I realized the rifle had move on the support from the rail to the FSB. I popped it back on the rail and was back hitting POA/POI again. I can understand the POI shift from the rail to the mag due how the rail/barrel install on the upper. The rail is like one big lever attached at the barrel nut that induces flex in the upper. I am sure Mr. LaRue did some testing with this and that is why he uses a proprietary upper receiver and rail. |
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Posted: 12/17/2011 6:03:49 AM EDT
[#38]
Quoted:
I'm more troubled by the difference between magazine, mid tube and unsupported points of impact than the muzzle supported. This proves that the Free float rail does not nullify the POI changes. As a #-gunner this can be detrimental considering the awkward and ever changing positions we shoot from. I guess the next test would be to see which rail and upper receiver combos result in the least POI changes. THIS. OP is better shooter than I for sure, but is it possible that the changes in POI are from nuances in using different fulcrum points as a rest - not from induction of barrel flex. As evidence, OP appears to be an excellent shot and is using FF handgaurds. Difference between using mid-support on his FF handgaurds and magazine release appears to be 1-2 MOA low. Neither of these holds are putting flex on barrel. |
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Posted: 12/17/2011 7:00:15 AM EDT
[#39]
I have noticed if i sight in with just my ff tube on the rest and my left arm at the butt stock it will shoot 2 inches higher than with my left hand on the tube or shooting off hand, resting on the barrel it shoot's even higher, anyone who dont belive this needs to try it for themselves. I always shoot with my hand on the tube now.
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Posted: 12/17/2011 7:51:52 AM EDT
[#40]
Quoted:
I would expect a monolithic upper to perform the same function as a FF tube- it prevents the barrel from contact that would interfere with harmonics or otherwise cause a change in poi. Think about how a sling on a standard forearm affects the poi when it is pulled tight when shooting. A non free floated forearm resting on sandbags or a hard surface should cause the same difference in poi as resting the barrel on it- although it should be less of a difference. Think about using a tree limb as a rest. You rest the forearm on it- not the barrel. That is also why precision rifles mount the bipod to the forearm and have the barrels free floated. it is to isolate the barrel from contact with the stock. Jim A monolithic upper performs the same function as a FF tube. The question is does it perform the function better? I do not know the answer to that question. While there may be little to no flex in the barrel, would there still be flex in the upper receiver? It would seem that a monolithic upper receiver would almost completely eliminate that. |
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Posted: 12/17/2011 8:35:33 AM EDT
[#41]
So does this mean loading the bipod will affect your POI, even with a FF rail?
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Posted: 12/17/2011 9:46:37 AM EDT
[#42]
Quoted:
So does this mean loading the bipod will affect your POI, even with a FF rail? I would not think so but I think it would depend on your BUIS setup. Let's say that you have free-floating rails but your front BUIS is set up on the rail and not the traditional front sight post (on the barrel). If there is flex in the free float rails (but not the barrel), your point of aim will still be off). The question: is there a difference in accuracy between free float rails vs. a monolithic upper in this case. I have a Colt M4 for duty use and a Noveske N4 with a VLTOR VIS upper (monolithic). The M4 that I use does not have free floating rails and based on the 25m zero targets I posted in this thread, the point of aim/impact does shift. The way I would zero is to rest the handguards on sandbags and grab the magwell for support. As you can imagine, this would stabilize the weapon, but it would cause a deflection. However, I have not experience that with my Noveske which has a monolithic upper. |
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Posted: 12/17/2011 10:26:06 AM EDT
[#43]
Quoted:
So does this mean loading the bipod will affect your POI, even with a FF rail? Even with a FF handguard there are forces being transmitted along the handguard to the barrel nut, and through that to the barrel. Freefloating the handguards decreases some of the pressure transmitted to the barrel, a monolithic setup would decrease the variable stresses even more. It does not eliminate the forces, just decreases them. A regular freefloated handguard will be more accurate than most people, some expert shooters will benefit from the additional step up to a monolithic system. |
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Posted: 12/17/2011 11:18:06 AM EDT
[#44]
Very interesting. I would suggest however, that in your next run of tests, you fire all of your groups from the same body position. I'm not trying to discredit your results, but your barrel-supported group was fired from a considerably different body position than the rest. Different stock position on shoulder, different strong-arm positioning, different angle of attack on pistol grip, among others. While these may appear inconsequential to some, as the cross-hairs were on the same spot, I would venture to say that they make more of a difference at range than many would think.
I also have to mention that I believe this is a drastic exaggeration of the POI shift as opposed to resting on a non-free-floated handguard. While there certainly is pressure on the barrel that is not present in a free-float set-up, this was resting on the muzzle device, which is very different than resting on a handguard. First, a handguard(in most cases) does not contact the barrel near the muzzle, but rather several inches back. Right there, you should be looking at a 30-50% decrease in the torque on the barrel, when compared to the muzzle rest. Secondly, a handguard has two points of contact, not just the one farther down the barrel. When you consider the fact that the handguard rests on the barrel-nut as well as the handguard cap , you are looking at further reduced pressures at the retaining cap, because the pressure is split between the contact points, and the pressure applied to the barrel-nut will be of virtually no-consequence. Again, I certainly appreciate your work, and these are very insightful results that you have here, but I just wanted to voice some thoughts and observations. |
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Posted: 12/17/2011 12:02:30 PM EDT
[#45]
Quoted:
Very interesting. I would suggest however, that in your next run of tests, you fire all of your groups from the same body position. I'm not trying to discredit your results, but your barrel-supported group was fired from a considerably different body position than the rest. Different stock position on shoulder, different strong-arm positioning, different angle of attack on pistol grip, among others. While these may appear inconsequential to some, as the cross-hairs were on the same spot, I would venture to say that they make more of a difference at range than many would think. I also have to mention that I believe this is a drastic exaggeration of the POI shift as opposed to resting on a non-free-floated handguard. While there certainly is pressure on the barrel that is not present in a free-float set-up, this was resting on the muzzle device, which is very different than resting on a handguard. First, a handguard(in most cases) does not contact the barrel near the muzzle, but rather several inches back. Right there, you should be looking at a 30-50% decrease in the torque on the barrel, when compared to the muzzle rest. Secondly, a handguard has two points of contact, not just the one farther down the barrel. When you consider the fact that the handguard rests on the barrel-nut as well as the handguard cap , you are looking at further reduced pressures at the retaining cap, because the pressure is split between the contact points, and the pressure applied to the barrel-nut will be of virtually no-consequence. Again, I certainly appreciate your work, and these are very insightful results that you have here, but I just wanted to voice some thoughts and observations. You can't shoot from the same position in each test... There is a big difference between shooting off the mag and shooting up on a block. Try it.
And the part in red is just wrong. Try it. I am uploading some new pics and vids that may help. Give me an hour with my shitty internet. lol |
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Posted: 12/17/2011 1:01:12 PM EDT
[#46]
Updated with new vid and pics of a SW MP with KAC Quad.
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Posted: 12/17/2011 1:25:52 PM EDT
[#47]
Quoted:
[snip] a handguard has two points of contact, not just the one farther down the barrel. When you consider the fact that the handguard rests on the barrel-nut as well as the handguard cap , you are looking at further reduced pressures at the retaining cap, because the pressure is split between the contact points [snip] The pressure will be distributed depending on what point the hand or stabilizing object is positioned along it, as well as how hard it is gripped or pushed down onto the object. This makes for dis-similar conditions which is exactly what destroys accuracy. I would even venture that most shooters put more pressure closer to the muzzle (from the center-point of the handguard) than on the barrel nut. I see your point about resting the muzzle on the barrier being an exaggerated example, but these groups were only taken at 50 yards. Even taking your assumptions of a 30-50% accuracy increase as gospel, extending this same test out to 100 yards would double or better the shift in point-of-impact. |
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Posted: 12/17/2011 2:50:13 PM EDT
[#48]
Updated with Vid and pics of a RRA Upper YHM FF Quad, EoTech, M855 (taiwan type)
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Posted: 12/17/2011 5:38:48 PM EDT
[#49]
Impressive to see how the three different configurations do.
Next. You'll have to try a 24" varnint.
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Posted: 12/17/2011 5:59:59 PM EDT
[#50]
Quoted:
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So does this mean loading the bipod will affect your POI, even with a FF rail? Even with a FF handguard there are forces being transmitted along the handguard to the barrel nut, and through that to the barrel. Freefloating the handguards decreases some of the pressure transmitted to the barrel, a monolithic setup would decrease the variable stresses even more. It does not eliminate the forces, just decreases them. A regular freefloated handguard will be more accurate than most people, some expert shooters will benefit from the additional step up to a monolithic system. So for real world precision shooting, it seems like a bolt rifle is a must. Unless of course, we have a new semi-auto that doesn't have the FF rail attached to the barrel nut. I always thought free floating an AR would give it magical powers so that any pressure to the handguards wouldn't affect POI. I guess I was wrong. 
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