Twist for 55 grain ammo?

allarile260

allarile260

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I've found a very good deal on an AR with a 1:8 twist, but I only shoot 55gr surplus. Would shooting that ammo wear out the 1:8 barrel very quickly? or should I go with a 1:7 or a 1:9? Most I'd expect out of it would be 1 1/2 MOA.
 
1 in 8 is a good compromise it should shoot 55-70 grain bullets very well, depending on the length of the bullets. Twist doesn't affect wear characteristics as much as material, lining or load pressures.
 
1:8 will work just fine with almost any bullet you would shoot out of an AR, as will 1:7. Fast twist barrels offer greater versatility with no major disadvantage.
 
All three twist rates will work fine for the 55 grainers.

I think it was an internet myth somewhere that 1/7 wouldn't stablize 55 gr bullets, but I have never seen an issue EVER in my LMT or any of my buddies rifles shooting 55 gr ammo.

I have read it on the interwebs but haven't been able to see in the real world.
 
enefgee said:
Be aware that Norc ammo has thrown bullets sideways at short ranges. The suspicion is that there are some undersize bullets in there.
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At the last service CQB match at Borden one of the other shooters on my target had at least 6 shots go through sideways, leaving perfect bullet profiled holes in the target. Shooting Norinco ammo very inconsistent groups.
 
My 24" bull barrel AR target rifle has a 1:10 twist. With light bullets like 52 gr. Sierra Match Kings I have achieved 5 shot 100 yard groups as small as .28". I have tried Federal Gold Medal ammo with 69 gr. Match Kings and the groups open up significantly (as target rifles go - around 1"). For my gun the bullet weight/twist rate/accuracy are definitely related. For a non-match barreled rifle I suspect the observed accuracy difference might be less noticeable.
 
Slower twists normally favour lighter (shorter) bullets. For military cartridges - what most folks shoot (55-62-70 grain) 1-in-7 to 1-in-9 twists work best. The early AR's came with a 1-in-14 twist.
 
Just watch that Norc ammo, run a magnet over the bullet (not the case), if it sticks don't use it. The bi-metal jacket will wear out your barrel very quickly. Twist rate will have little effect on wear.

Fast twist rate will stabilize longer (typically heavier) bullets better than slower twist. As long as your bullet is designed to handle the higher RPM without coming apart a fast twist will be fine with any weight of bullet.
You can't overstabilize but you can exceed the bullets design RPM.
I shoot 55gr FMJ from my 1:7 all the time with no issues.

Good luck
 
cr5 said:
Just watch that Norc ammo, run a magnet over the bullet (not the case), if it sticks don't use it. The bi-metal jacket will wear out your barrel very quickly. Twist rate will have little effect on wear.

Fast twist rate will stabilize longer (typically heavier) bullets better than slower twist. As long as your bullet is designed to handle the higher RPM without coming apart a fast twist will be fine with any weight of bullet.
You can't overstabilize but you can exceed the bullets design RPM.
I shoot 55gr FMJ from my 1:7 all the time with no issues.

Good luck
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Do they normally specify if steel? or you just take your chances
 
bluesclues said:
I think it was an internet myth somewhere that 1/7 wouldn't stablize 55 gr bullets,

.
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No the claim is that a 1 in 7 overstabilizes 55grain bullets. I don't think you can overstabilize a 55gr bullet but when you go lighter like 35 to maybe 45gr varmit bullets you can overspin them in a 1 in 7 where the bullet can breakup in the air. Any 55gr bullet I've used in my 1 in 7 twisters has been fine (55FMJ and SP)
 
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