Question about twist rates and supersonic bullets.

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

Moderators: gds, bakerjw, renegade

22_boomer
Silent Operator
Posts: 50
Joined: Sat Mar 10, 2012 6:08 pm

Question about twist rates and supersonic bullets.

Post by 22_boomer »

I've played for years with a smaller 30 caliber cartridge that I've use bullets like the 110gr Barnes TSX on up to the 155gr Sierra Palma Match. I wanted to move up in cartridge size and try the 300 BLK and wondered if barrel makers might start making barrels with a little slower twist rate -- something in the 1:10 or 1:11 twist rate for those that just want supersonic. I'm shooting through a 1:10 twist barrel now and like the accuracy -- I just want to upgrade the power level.
User avatar
300Blk
Site Admin
Posts: 7331
Joined: Mon Apr 25, 2005 9:31 am
Location: USA

Re: Question about twist rates and supersonic bullets.

Post by 300Blk »

Sure - any barrel maker can just use a 308 blank and do that.

For me I would still want 1/7, even if it were just for supersonic, because it helps the bullets expand on impact.
22_boomer
Silent Operator
Posts: 50
Joined: Sat Mar 10, 2012 6:08 pm

Re: Question about twist rates and supersonic bullets.

Post by 22_boomer »

300Blk wrote:Sure - any barrel maker can just use a 308 blank and do that.

For me I would still want 1/7, even if it were just for supersonic, because it helps the bullets expand on impact.
I will say that I have had second thoughts about going with a barrel that was non-standard and that bit of info about expansion is just another reason to go with the standard.
bearman
Silent Operator
Posts: 73
Joined: Sun Feb 06, 2011 3:42 pm
Location: southwest VA

Re: Question about twist rates and supersonic bullets.

Post by bearman »

When are we going to see the 1/7 AAC barrels for sale? I am waiting on a 16" ar barrel.
User avatar
300Blk
Site Admin
Posts: 7331
Joined: Mon Apr 25, 2005 9:31 am
Location: USA

Re: Question about twist rates and supersonic bullets.

Post by 300Blk »

I don't know. That is up to the production manager.
Taseal
Senior Silent Operator
Posts: 108
Joined: Tue Mar 27, 2012 3:23 pm

Re: Question about twist rates and supersonic bullets.

Post by Taseal »

300Blk wrote: For me I would still want 1/7, even if it were just for supersonic, because it helps the bullets expand on impact.
I wish this was decided on from the beginning =/

but then again, things never end the way they start.

Most people are waiting on 1:8 barrels, and 1:7 isn't even in sight yet, but we have SMEs saying 1:7 should be wtg
s&wblkshooter
New Member
Posts: 1
Joined: Mon Mar 26, 2012 7:35 pm

Re: Question about twist rates and supersonic bullets.

Post by s&wblkshooter »

Does twist rate have anything to do with accuracy/group sizes? I recently purchased an M&P15 that shoots either 300 whisper or blackout. and the best that I have been able to get is a 3 1/2" group at 100 yds, using both factory Hornady ammo and handloads. My belief has always been that a fast twist rate is meant to shoot the longer heavier bullets. My .308 bolt gun has a 1-10" twist rate and it shoots 150-168 grain bullets really well, but not so much the lighter bullets. Anybody have any insight into my dilemma?
User avatar
CoheedKillgannon
Silent But Deadly
Posts: 193
Joined: Sat Dec 24, 2011 3:28 pm
Location: New Jersey

Re: Question about twist rates and supersonic bullets.

Post by CoheedKillgannon »

With 125 grain Remington Premier Match and 115 grain Remington UMC ammo I have been getting great groups from my 1 in 8 twist Noveske barrel.
User avatar
300Blk
Site Admin
Posts: 7331
Joined: Mon Apr 25, 2005 9:31 am
Location: USA

Re: Question about twist rates and supersonic bullets.

Post by 300Blk »

Well, we have done 50 round groups with the 1:8 barrels from test fixtures. That is 10 groups of 5 shots per group. The average at 100 yards - 0.85 inches. The twist is not a problem to accuracy, assuming the bullets and barrel are otherwise good.
User avatar
velo555
Silent But Deadly
Posts: 391
Joined: Wed Mar 28, 2012 9:14 am
Location: Upstate SC

Re: Question about twist rates and supersonic bullets.

Post by velo555 »

300Blk wrote:Sure - any barrel maker can just use a 308 blank and do that.

For me I would still want 1/7, even if it were just for supersonic, because it helps the bullets expand on impact.
I don't know alot about custom barrel makers. Who would be a reasonable and trustworthy barrel maker for a 1/7 SBR barrel to be made from a 308 blank? Also can we get a petition going to send to the production manager to help him decide to switch over production to 1/7 units.
Victor Lopez
Post Reply

Who is online

Users browsing this forum: No registered users and 62 guests