300BLK bolt gun accuracy in supersonic?

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HankC

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I have a 7.62x39 bolt gun built on a Turk K Kale mauser action, like it a lot. While 300BLK is close to 7.62x39 performance I wonder if 300BLK bolt gun would be a good idea. I don't hunt, don't shoot long distance, so I don't need another powerful round while I have a few 308s already. I just like bigger holes on paper! 300BLK brass can be converted from cheap and abundant 223 brass, 7.62x39 brass or brass case ammo is expensive. I reload so I don't buy 300BLK ammo. I heard Savage abandoned 300BLK because it is not up to the accuracy expectation. I have a 300BLK AR and it is not as accurate, with 125 gr Speer TNT, as my 223 ARs. I only shoot in supersonic. I think fast burning powder in 300BLK may have an effect on accuracy. Anyone has experience with 300BLK bolt gun accuracy? I likely only shoot supersonic within 100 yds. My home built 308 heavy barrel bolt gun built on mauser action can put 168 gr in one hole and not sensitive to load, so are my 223 bolt guns and my home built 7.62x39 bolt gun is not far behind. Wonder if I should consider a 300BLK bolt gun. If not accurate or difficult to load to accuracy, I won't bother.
I know some folks would say 300BLK only make sense if subsonic, I may play with some subsonic but most likely supersonic, we can leave subsonic out!
 
Most of the people I have talked to on the subject have said sub moa is very easy to achieve in a good bolt gun such as the ruger american. My 300 blackout AR is right around moa. Probably about 1.25 moa.
 
I wonder if some of the issue is the vagaries induced by cutting a 223/556 case below the neck then running it thru a full length die. Most cartridge that you do that to also gets more work to make them concentric. I dont know anyone who does that with the blackout.

With factory blackout brass handloqds, and sig ammo, my RAR shot right around 1". Which is about as good as i can do with the 4x shotgun scope i used on it.

If you already have an x39 that shoots well, i dont think theres a huge reason to switch to the blackout, unless you want to build another gun. If so id consider it worthwhile to see how accurately you can get the blackout to shoot, I don't know anyone who's realy pushed it for top accuracy.
If your only shooting suppers you may want to see if you can get it short throated, and or run longer heavier projectiles.
 
I heard Savage abandoned 300BLK because it is not up to the accuracy expectation.

I doubt that was the real issue unless they had issues with factory ammunition. There's a problem shooting factory Blackout ammunition in bolt action rifles and the problem is that it's hard to make .300 Blackout brass well that will headspace correctly due to the very small shoulder. I worked for Remington for two years and developed a Blackout load while there and making the brass gave us all manner of stress. I've encountered light strikes and misfires with numerous brands of factory ammunition in bolt action rifles with Blackout chambers where the bolt will barely close on a GO gauge. I've found factory loads with the shoulder set back as much as .020" below SAAMI spec. 300 Blackout factory ammunition is better suited to AR15s/M4s. Bolt action rifles are far more reliable and accurate with handloads using brass that has been fire formed to the chamber. Basically, if you're going to buy a bolt action 300 Blackout you should plan on reloading for it whether subsonic or supersonic since factory ammunition will most likely be problematic. Consistent sub moa groups with supersonic ammunition from a bolt action rifle is easy to achieve with reloads but factory ammunition can be all over the place with a great group one minute followed by a 3" group the next.
 
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If you have a 7.62x39 rifle that shoots well, I concur with @LoonWulf that it doesn't make sense to get into 300 BLK. You can buy a ton of brass for your 7.62x39 with half of what it costs to buy a new bolt gun. And components are cheap, there are many people who have great results with .308 bullets in .311 bores, so I really don't see for what you stated was your desires the point of a 300 BLK. The 7.62x39 is going to have better energies and is the better cartridge in supersonic loads IMHO.
 
I heard Savage abandoned 300BLK because it is not up to the accuracy expectation.

If your focus is on super-sonic accuracy... you have nothing to worry about. They actually had trouble getting accuracy out of their sub-sonic loadings.
http://www.thetruthaboutguns.com/2012/04/foghorn/savage-scraps-300-blk-rifle/

These guys made a competition out of shooting subs at distance....good load data & info to be had.
http://www.300blktalk.com/forum/viewtopic.php?t=98191
Ultimately Vihtavouri N110 & N120 are two of the better powders for heavy subs.


I have a 300BLK AR and it is not as accurate, with 125 gr Speer TNT, as my 223 ARs.
What's your load data on that ammo if you don't mind my asking....
 
I bolted together a Savage 10 in 300AAC a while back, to go with my 300AAC AR's. I built the 300AAC rifles to replace my 6.8SPC and 7.62x39 sporting / defense rifles, expecting only to shoot supersonic ammo. I can see no sporting / defensive badness in a light handy 30-cal rifle pushing a 125gr bullet fast enough for a MPBR / 800+ FP of energy to 200 yards or better.

It's a fun walk-around rifle. It'll keep between 1 - 1 1/2 MOA with my bulk load 125gr Sierra SPs, which is plenty good for sporting and defensive use within the useful range of the chambering. It's not as accurate as my heavy long range guns, but that's not its purpose.
 
What's your load data on that ammo if you don't mind my asking....
16.5gr H110, 125 gr Speer TNT, 2.09" COAL, converted LC brass, out of 16" carbine length gas system. The brass are loaded first time after conversion, my friend said that may have an effect on accuracy due to residual stress, second loading may improve, don't know. Now the rifle shoots US Quarter size at 50 yds with Speer TNT. Good enough for fun, but nothing to brag about. For a light recoil round, I expect better. My 308 and 223 ARs with good bullets can do better.
 
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You might have feeding problems converting from 7.62 to .300 BO as the case rim is smaller. If you go to all of that trouble, consider that rebarrelling to the 6.8 SPC or 6.5 Grendel (even the new Valkyrie) which all have case head diameters very close to that of the 7.62x39. All have superior longer range ballistics compared to the .300 BO or 7.62x39 and inexpensive factory ammo is readily available.
 
I’ve had 0 issue with moa cast lead subs in AR 300 blk rifles. I’d expect better from a bolt gun.
 
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