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Posted: 10/10/2010 11:01:13 AM EDT
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This thread was a close call between the reloading and the suppressor forums. I chose here b/c the "subsonic" part seems to make it more relevant.
I've been working up subsonic .308 loads. The internets are not very helpful thus far, with information of questionable quality spread everywhere. I thought this thread could be a good place for people to list their loads. Here's two I have worked with: Bullet: Hornady 180 gr roundnose Brass: Winchester .308 brass Primer: Fed 210M Length: 2.650 Powder: Trailboss 11.0 gr Velocity: ~1035 fps @ 80 degrees F Rifle: Remington 700 tactical, 20" barrel, 1/10 twist, threaded by GA Precision with AAC Cyclone Accuracy: 2 MOA (hold point from my full power load is at second mil-dot) Bullet: Hornady 220 gr roundnose Brass: Winchester .308 brass Primer: Fed 210M Length: 2.650 Powder: Trailboss 13.5 gr Velocity: ~1050 fps @ 80 degrees F Rifle: Remington 700 tactical, 20" barrel, 1/10 twist, threaded by GA Precision with AAC Cyclone Accuracy: 2.5 MOA, BUT though this load appears stable at 20 yds, there is apparent keyholing at 100 yds. I have stopped using it. I have experimented with drilling the flash hole to 9/64", but found that it resulted in increased inconsistency. I have also experimented with large rifle magnum primers, in both drilled and undrilled flash hole cases, and also did not notice any benefit. Would appreciate others' load data; please include info about your rifle for others to use as a reference. |
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I have tried this and my accuracy is under 1 MOA
Bullet: 180 Spitzer - Flat Base - Not BT Brass: LC .308 brass Primer: CCI Length: within spec Powder: Trailboss 10.5 gr Velocity: Not sure, but below Speed of Sound @ 80 degrees F Rifle: Remington 700 tactical, 20" barrel, 1/12 twist and Remington 700 Heavy barrel cut down to 16" also 1/12 twist both using a Coastal LRT can Accuracy: <1 MOA No hold over as I use them dedicated to sub ammo. Works great, Trial boss smells a little bit but i am happy with my accuracy. |
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Quoted:
I have tried this and my accuracy is under 1 MOA Bullet: 180 Spitzer - Flat Base - Not BT Brass: LC .308 brass Primer: CCI Length: within spec Powder: Trailboss 10.5 gr Velocity: Not sure, but below Speed of Sound @ 80 degrees F Rifle: Remington 700 tactical, 20" barrel, 1/12 twist and Remington 700 Heavy barrel cut down to 16" also 1/12 twist both using a Coastal LRT can Accuracy: <1 MOA No hold over as I use them dedicated to sub ammo. Works great, Trial boss smells a little bit but i am happy with my accuracy. I assume you are using something like the Hornady interlock 180 SP |
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More data I've found, not tested by me.
From Hodgdon: Bullet: 168 gr Sierra MatchKing Primer: Fed 210M primer Powder: 8 gr of Clays COAL: 2.8" Velocity: 1060 fps Bullet: 168 gr Sierra MatchKing Primer: Fed 210M primer Powder: 8 gr of TiteGroup COAL: 2.8" Velocity: 1080 fps From elsewhere on internet: Bullet: 173 Grain GI Match (?) Primer: WWLR Powder: Trailboss Velocity (1025 (9.4 gr)); 987 (9.0 gr)) Bullet: Hornady 180 gr RN Primer: CCI benchrest Powder: Trailboss Velocity: (950 fps (11.0 gr.); 1050 fps (11.4 grains)) Gap SP (lite) rem700,Rock 20" 1-11.27 (or whatever) Srt Shadow brass : LC std. primer: CCI 250 powder: Trail Boss 10.6gn bullet: 190 SMK OAL : 2.810 FPS : 1055fps 1.5" at 300yds 10.5 gr Greendot Win LRM primers Remington brass 220 Hornady RN 1030-1080 fps need to raise rifle barrel to get all powder against primer for best consistency 3/8" 10 shot group at 100, 2" at 200 12.5 gr trailboss Win LRM primers Remington brass 220 Hornady RN 1010-1020 fps 1/2" at 100, 1.5" at 200 10" 1/8 twist shillen encore pistol barrel 240 SMK 14 gr Trailboss Win LRM primers Rem brass 1020-1050 fps 1" group @ 100 (PISTOL) *Subsonic Load* Hornady 180 RN Federal brass Fed 210 primer 8.6gr vv N320 2.650" OAL Avg vel=1022fps @ 48*F |
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still experimenting with loads so this is of interest for me as well. it appears in my rifle anyway, that boat tail bb's dont seem to do too well. thought i had a great load of 9.8-9.9 grains of Trail Boss over 165 BTHP Sierras (#2140's)....they shot one-hole groups at 35 yards but key-hole at 100. MV was right at 1075fps and nice and quiet. have tried 220SMK's, 210VLD's and 165 BT Noslers with tumbling issues. I ordered some 180gr Speer round nose (#2047's) and will try them. they are a flat based bullet and long, so hopefully they will stabilize and low velocities. have experimented with 110gr bb's and accuracy is so-so but they definately dont key-hole at distance. 170gr flat point hunting bullets work well but arent great accuracy wise as i was about 2 1/2 MOA at 100 yards. i guess careful experimentation is the key to success here....will keep this thread alive by posting results if i get out this weekend to play a bit.
Rem 700 Schneider 16-inch 1x10 twist Amer Mfg Triple-X Lapua brass Fed mag primers 
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| I have had great luck with a Hornady 170 grain round nose w/ flat base with the Trail Boss load listed above. I have used a few different loads and it has had very good accuracy and will stabalize well in the standard Remington barrel. While most people load at 1040 fps, drop it down to 990 to 1010 fps and you will be surprised at accuracy and the db level will drop also. |
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Everything I have seen appears to indicate that either roundnose or spitzer bullets, in the 170-180 gr range, appear to be the way to go. Besides, I wouldn't be very interested in anything lighter than that, since I'd like to keep the bullet energy high.
As I noted above, 220 gr bullets will work but with highly questionable stabilization. When the holes at 100 yds look more like rectangles than circles, I become very concerned. I should also be out at the range this weekend and will post more data. Does anyone have any powder suggestions other than Trailboss? TB does seem ideal given its burn rate and volume... |
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I'm still experimenting with seating depth re: accuracy.
One thought, completely unproven as yet, is that a lower seating depth decreases the amount of empty space in the case, possibly increasing the consistency of powder burn. I have also read that decreased COL up to a point can lead to lower overall pressures, effectively because the bullet is not starting on or next to the lands. Again, this is just my compilation of tons of info spread out over the internet (possibly crap), so it is only a working thought at this point, and I very well may be wrong. Will keep this thread alive in hopes we can pool collective wisdom/experience. Once we develop a load, I'd be very interesting in talking about terminal performance. Think suppressed varmint hunting with .308. |
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I've loaded/shot a fair amount of subsonic .223 and .308 for use with various rifles on a pair of YHM phantom cans. I haven't had the chance to actually make a kill on any local varmints yet, but I have pulled a couple of the .223 bullets out of a tree. The tree was about 100yds from the firing position and the bullet was lodged to it's own depth and only slightly deformed. It was a 55gr Nosler BT and the plastic tip was still on and intact. I think the terminal ballistics of subsonic .223 are about the same as .22lr if I had to guess. My .308 sub load is 180gr round nose. They shoot fairly well. I will add that I have started loading them further back than 2/1000's off the lands. The first few I tried were loaded to the same specs as my match loads, right about 2/1000's off the lands. I use a Hornady LNL measuring tool that uses each bullet to measure the overall length to the lands and then you back it off however much you desire. I found that loading just 2/1000's off the lands got me the first few bullets stuck in the barrel. Once I started setting them back a bit, no more problems. IIRC, I'm more like a couple hundredths back from the lands. I'd have to go look at the load sheet to remember. I'm all out of those bullets so I gotta find another source of cheap round nose in about the 180gr weight. FWIW, I had poor results trying to load up 168gr SMK's subsonic; I gave up on that plan. |
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Your experience with stuck bullets would seem to corroborate what I thought re: increased pressure and the negative effects of full-length seating.
One analogy I heard is that of a truck jumping a curb. Put the truck against the curb and it takes a lot of pressure to get the wheel over the curb. Give the truck a running start and it isn't that difficult. Similar analogy as to seating right on the lands vs. giving it a further "jump". Again, pure speculation and worth what you paid for it. Next test will be 180 RNs vs. 180 SPs. I might even mix up some home made ballistic gellatin. |
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Your analogy of the truck on the curb explains pretty much exactly the theory/conclusion I came to. I was figuring there wasn't enough pressure being developed to push the bullet out without it getting a running start. Once I set 'em back a bit, they got the running start needed and it all works fine. |
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some success trying loading to OAL....thanks
180gr Speer Soft Points/flat based bb's. 10.3 gr Trail Boss. one hold groups at 30 yards and will try at 100 yards this weekend and will report back. Also trying some 125 Speer TNT's and 135SMK's as well. using 7.5gr TB to push them at 1025fps testing them in the side yard today. 168 SMKs keyhole and tried loading them backwards and still keyholed. Rem 700 Schneider 16-inch 1x10 twist Amer Mfg Triple-X Lapua brass Fed mag primers |
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I'd be interested in how the lighter bullets perform; though, generally speaking, I've tried to focus on 170+gr bullets since I'm already losing a lot of energy going subsonic.
I tried to load several bullets backwards, but they were simply too small –– I wasn't going to jam them into the case just for the sake of experimenting. If anyone has any good "backwards bullet" loading data, I've never seen it. Eventually I am going to make some homemade ballistic gellatin to test the best loads we develop. I'll have some more data available to publish soon. |
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This is great info; I started working up a 7.5x55mm (Swiss) subsonic load for suppressed use, but got spooked when I got down to 12 grains of Trailboss and stopped, as it seemed there was an awful lot of smoke hanging around in the barrel (I'd pull the bolt to check if the bullet cleared the barrel, and I'd have to blow the smoke out to check). If that's normal, I'll go on with my 11 grain load, but the larger-than-.308 case size and similar ballistics tell me I'll have even more trouble getting bullets subsonic and stabilized (the rifling is 1:10.6).
Is the high amount of smoke normal? |
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Quoted:
This is great info; I started working up a 7.5x55mm (Swiss) subsonic load for suppressed use, but got spooked when I got down to 12 grains of Trailboss and stopped, as it seemed there was an awful lot of smoke hanging around in the barrel (I'd pull the bolt to check if the bullet cleared the barrel, and I'd have to blow the smoke out to check). If that's normal, I'll go on with my 11 grain load, but the larger-than-.308 case size and similar ballistics tell me I'll have even more trouble getting bullets subsonic and stabilized (the rifling is 1:10.6). Is the high amount of smoke normal? I had this happen on a 308 load once. I pulled the bolt and had to blow the smoke out to make sure something wasn't wrong. |
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Bullets like the typical 168gr HPBT are quite poorly balanced. They have a long slender nose and a fat back end. Even flying backwards they are difficult to stabilize. Either stick with lighter stuff or go heavier but stumpier like a 180 or 200gr round nose. As some people have discovered, subsonic flight stability decays with distance. This is the opposite of supersonic flight stability. The concept of "muzzle energy" is a moot consideration when discussing subsonic terminal ballistics. Subsonics don't expand and have a tendency to hugely overpenetrate. I have done terminal testing with a 150gr subsonic and found it to easily penetration more than 16" of wet phonebook, then blow through the bottom of the bucket and disappear into the dirt far enough to be unrecoverable. In a soft, wet target even a middleweight subsonic is going to fly out the backside of the target, taking a ton of energy with it. Making that bullet even heavier will just result in even more energy being wasted out the back side of the target. |
You are correct about over penetration. You should see what a 240 grain Match King will do in my 300-221. Those things are like freight trains, they just keep on going. They will penetrate steel plate with ease, and will go the full length of a deer with ease. When shot like that, they don't go far!
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Quoted:
Bullets like the typical 168gr HPBT are quite poorly balanced. They have a long slender nose and a fat back end. Even flying backwards they are difficult to stabilize. Either stick with lighter stuff or go heavier but stumpier like a 180 or 200gr round nose. As some people have discovered, subsonic flight stability decays with distance. This is the opposite of supersonic flight stability. The concept of "muzzle energy" is a moot consideration when discussing subsonic terminal ballistics. Subsonics don't expand and have a tendency to hugely overpenetrate. I have done terminal testing with a 150gr subsonic and found it to easily penetration more than 16" of wet phonebook, then blow through the bottom of the bucket and disappear into the dirt far enough to be unrecoverable. In a soft, wet target even a middleweight subsonic is going to fly out the backside of the target, taking a ton of energy with it. Making that bullet even heavier will just result in even more energy being wasted out the back side of the target. This is extremely interesting, and merits more research. Has anyone ever tried swaging their own bullets for this application? |
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