Comments on: 300 Blackout Basics — Specs and Cartridge INFO

By: Bruce

Bruce — Sun, 11 Oct 2020 10:02:29 +0000

Twist-rate!

7.62 x 39 usually runs in barrels with a 1:10″ (ish) twist. This is actually much tighter twist required to stabilize the short 124gn. bullets. It happened that way because when the Russians developed the round, all of their 7.62mm barrel making machinery was built to make 1:10″ twist barrels for a bazillion Mosin Nagants and a swag of machine guns in 7.62 x 54R. Note that they used exactly the same twist on the TT30 and TT33 auto pistols and millions of SMGs chambered in 7.62 x 25. It seemed to work OK for all those years.

However, if you try to shoot “custom” loaded 7.62 x 39 ammo loaded with a 220gn bullet from a 1:10 twist barrel, you will be disappointed because the bullet will not be DRIVEN fast enough to SPIN fast enough to stabilize correctly.

Thus, “proper’ 300 BLK and .300 Whisper, before it, run with tighter twist barrels. 1:8″ or increasingly, 1:7″, especially if you want to stabilize subsonic, LONG bullets at low temperatures. The LAST thing you want is a “wobbly” bullet going through your expensive muffler, not quite behaving itself.

Lighter, 125gn bullets won’t care, but long, slow bullets need FAST spin-rates.

By: TXWheelgunner

TXWheelgunner — Thu, 21 Feb 2019 17:47:48 +0000

Spend the money on a decent upper. It’s a 30 second swap from 300blk to .556
I have a Sig red dot on my 556 upper and a 4-12×40 Bushnell scope on my 300. Best of both worlds. I don’t shoot subsonic. FWIW.

By: Wilson

Wilson — Sat, 17 Nov 2018 15:20:44 +0000

Dennis- 300 BLK starts with a 5.56 casing that they neck down much shorter, allowing for a wider and longer bullet that can now weigh significantly more than any 5.56 can. And using the 5.56 casing and same length round (from casing base to bullet tip) means they can use 5.56 magazines with no capacity loss. 7.62 has a wider casing and requires different size magazines along with a different bolt. 300 BLK was a way to achieve similar ballistics as the .308- with the least modifications to your 5.56. All you need is a bigger diameter barrel. So you can ball on a budget and just buy the barrel and make the swap when needed-or buy just brand new upper already setup for 300 BLK and throw it on your existing lower. Either way you go it is cheaper and requires the least modifications-while providing far superior performance and effectiveness over 5.56 in certain scenarios.

By: Mike

Mike — Sat, 15 Apr 2017 15:21:19 +0000

Dennis, running 7.62×39 in an AR has a whole bunch of issues on its own.

By: Bo Guss

Bo Guss — Fri, 14 Apr 2017 07:37:37 +0000

With a warm barrel/suppressor unit, it is possible to shoot impressive groups. Out of a cold unit, you will always have a flyer, usually the first shot.

By: NineWays

NineWays — Thu, 13 Apr 2017 16:09:49 +0000

Though it’s a common report that subsonic ammo isn’t remarkably accurate for most users, I’ve been very pleased with my Remington 700’s performance with 208 AMaxs.

By: Dennis Santiago

Dennis Santiago — Thu, 13 Apr 2017 15:46:46 +0000

The question that I’ve always asked when I look at this is is why hasn’t someone figured out one can just as easily make a modern set of 125gr and 220gr 7.62×39’s and blow away the .300 BLK at it’s own game?