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1/25/2018 7:38:29 AM
Posted: 7/9/2002 8:38:31 AM EST
I would like to buy a sig 551 ; most of the time i will shoot 55gr fmj and ss109 ammo.
Which barrel twist do you advice me between 1:10 and 1:7 ?
does 1:7 barrel twist really wear the barrel ?
Link Posted: 7/9/2002 10:13:36 AM EST
Link Posted: 7/9/2002 10:24:52 AM EST
1:9 is the lowest for the range of lengths of .223bullets in the 55 to 62 grain weight range. As the Bee Keeper said, 1:10 is optimal for bullets with lengths in those weight ranges.

Noah
Link Posted: 7/9/2002 10:52:02 AM EST
I know that the 1:10 will stabilise bullet up to 69gr , but i have also read that the ss109 heve the same lenght that a 71 grs lead core bullet !
Does the short barrel of the 551 require a faster twist ?
Link Posted: 7/9/2002 11:06:04 AM EST
In the AR, the optimum barrel twist for the 55 grn bullet is 1:12.
On the other hand the optimum bullet is 62 grn for a 1:9.
Link Posted: 7/9/2002 1:20:22 PM EST
Link Posted: 7/9/2002 5:18:02 PM EST

Originally Posted By 5subslr5:
In the AR, the optimum barrel twist for the 55 grn bullet is 1:12.
On the other hand the optimum bullet is 62 grn for a 1:9.



I'm curious where you got your info?
Link Posted: 7/9/2002 5:46:19 PM EST
I always use 1/9 because it will stablize and shoot accuratly the 62gr. SS109 such as C77 or M885 and it will also give excellent accuracy with the cheaper 55gr. bullets.

1/7 is the twist rate nessecary to stablize the governments tracer round. It is very long and thus require a 1/7 twist to stablize. You don't need the faster 1/7 twist, unless you will be shooting very heavy match ammo like the 75gr. stuff.
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