Gunsmithing 308 bolt action pistol sub/reduced load twist rate.

[BuildItYourSelf]

Hello.
I am looking for anyone with experience with a 308 short barrel (mine will be a 10.5" pistol) that is primarily used with heavy subs and reduced loads. 220smk subs and reduced loads with hunting bullets anywhere fron 175gr - 220gr.
I was thinking 1/8 would be just about right but i would question its performance with a normal load like a 175smk at 2600fps in most rifles.
It will be intended for a compact, light, packable, short range, 200yard is a rare shot on whitetail in the woods of PA, bolt action pistol.

If I can keep tight groups with subs out to 100y and with reduced loads out to 200y I'll be happy. But if I can get 400y at 1moa with whatever load I need to develop to achieve that I would be even more satisfied with the build.

The pistol will be like the 700cp with a folding brace. But it will be a stainless receiver and most likely a mcgown remage barrel.

Anyone with experience on such a matter please feel free to comment. I would also be interested in any load data you may have on fast twist short barrel 308.

Thanks.

 

[Red_SC]

With the arrival of the .300 Blackout, the popularity of the subsonic and reduced power .308 Win has almost disappeared. It used to be discussed a lot, but I haven’t played with it or seen anyone else doing it in quite a while. Liberty used to make reduced capacity brass to alleviate the low powder density issues, but that’s long gone. Trailboss will help.

As far as barrel twist and such, the bullets and velocities you’re looking at are similar to the Blackout, so that data should translate.

 

[biffj]

1-8 is a good twist rate for subs and while some will tell you that it will kill your accuracy with "normal" 308 loads it will be fine. Use good quality bullets for high velocity stuff and your accuracy problems will be few. With the 10 " barrel you'll have other issues first. The biggest one is finding an accurate powder for a case that is way over capacity for subs. Running the blackout is a much better solution and the range of useable velocity is a lot wider with commonly available powders.

Frank

 

[kindabitey]

Hello.
I am looking for anyone with experience with a 308 short barrel (mine will be a 10.5" pistol) that is primarily used with heavy subs and reduced loads. 220smk subs and reduced loads with hunting bullets anywhere fron 175gr - 220gr.
I was thinking 1/8 would be just about right but i would question its performance with a normal load like a 175smk at 2600fps in most rifles.
It will be intended for a compact, light, packable, short range, 200yard is a rare shot on whitetail in the woods of PA, bolt action pistol.

If I can keep tight groups with subs out to 100y and with reduced loads out to 200y I'll be happy. But if I can get 400y at 1moa with whatever load I need to develop to achieve that I would be even more satisfied with the build.

The pistol will be like the 700cp with a folding brace. But it will be a stainless receiver and most likely a mcgown remage barrel.

Anyone with experience on such a matter please feel free to comment. I would also be interested in any load data you may have on fast twist short barrel 308.

Thanks.

1-8 will stabilize most everything
Trailboss is your friend for 308 subsonic

 

[BuildItYourSelf]

I do currently load 308 subs with trailboss. I still have about 5lbs of it.
I also have a few 300blk and load for them.
I am Aware 300blk is the best choice for subs. But the reason I am choosing 308 in this build is because Its a bolt gun and the extra inch on throw is a non issue. Plus it would be an extra $150 for me to to get a blank stainless receiver and then replace the bolt for 223. Also it's cheaper to use aics mags for 308 in a r700. I understand I can use aics mags with 223 and 300 blk. But the 300 doesn't function well in that set up. I know because I tried everything. So I would was bottom metal that uses an ar pmag. That's an extra $200 on the build.
And even after all that I would believe I will have better luck trying to get 1moa out to 400 yards with enough ass to drop a whitetail using a 308 case VS 300blk.

Really my concern is with a short barrel 10.5" I will have alot of time finding a powder that will be almost completely burnt when the bullet leaves the barrel and also achieve say 2200fps without a dangerous peak pressure. Im thinking a ball powder like bl-c2 and a 250 cci is a good start. But perhaps faster stick will work as well. I would imagine 30-30 and similar will be good for referring to. I really want to find something that works before I try h110 or 1680 in the 308 case. I believe I will have inconsistent ignition and a wide velocity spread. Keep in mind I'm not talking about sub loads right now. I have that load data down pat. I'm grouping a touch over 1" in a 20" 1/10 using 180gr Hornady. And not much wider with the cheap Rainer. Also my dope track is in point.
I can hit 500m rams 4 out of 5 no problem. Obviously they don't hit hard. But it's proof of an accurate flight path dispite its going end over end by then. I have no keyhole at 200m at all with them. I'm excited to see what a 1/8 will produce for me after developing.

 

[BuildItYourSelf]

I'm going to disagree with the sub statement. My 308 subs on trailboss are far more consistent and accurate then I got my 300blk to be. The big benefit on a 300 blk sub is you can cycle an ar and keep the velocity down. No way 308 on trailboss can do that because the pressure doesn't really spike like h110 does in a heavy sub load.

I have zero concern with 308 sub ammo development for this project. I fired a few 220gr smk on top of 10gr of trailboss with a 250cci from a 10" contender and the flash wasn't very big. And shooting through a beer box 2 feet away there was little powder burn marks so I believe the powder is pretty much with the barrel length. Where as a 300blk typically throws unburnt powder out of 10" and I can most definitely tell its still burning in my can on my AR pistol.

I'm far more concerned with getting a good "normal" load developed for this then a sub load.