Twist rate/bullet weight in AR-15

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awilson0407

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My AR-15 has a 1:7 twist and I have several cases of 55 gr. USA ammo. My initial (and pretty much only) experience with accuracy was horrible when shooting this rifle to qualify for a CMP M-1 Garand. I'm not at all sure it is sighted in correctly. My question is...is 55 gr. ammo suitable for a 1:7 twist? Or do I have a lot of ammo that is a mistake? Sorry if this topic has been beaten into the ground previously. Thanks.
 
55 gr is marginal for a 1:7 twist barrel. 1:9 would be better. Or, if you're looking for ammo for your 1:7, try 62gr. and up.

Also, the ammo could just be cheap, bargain ammo.

Where are you located? If you own no 1:9 uppers, I'm sure someone near you would be willing to take the ammo off your hands.

Mike
 
if you're qualifying for CMP, i'm assuming you're shooting the cmp course of fire. if you were shooting it at 200 yrds, or further, then yeah, 55g is going to suck for that. usa ammo is crappy ammo, so it's going to suck more. i very much doubt you would notice the difference in 1/7 and 1/9 twist on paper
 
I've shot 52gr SMKs out of a 1:8 with good results.

A crappy bullet isn't gonna fly as well as a match grade bullet no matter what the twist rate is. A friend of mine shot those 55 grain Winchesters at a local high power match and couldn't hold the target at 300 yards.
 
Here's some info that may be helpful. Ths chart indicates what is usually the optimum for a barrel but doesn't mean that it won't shoot higher or lower grian bullets...it's not set in concrete:

.224 / 5.56mm
1:16 up to 55 grains
1:15 up to 55 grains
1:14 up to 55 grains
1:12 35 – 63 grains
1:9 45 – 69 grains
1:8 55 - 75 grains
1:7 62 - 90 grains
 
True, but for the purposes of this discussion (.223 out of an AR), the two are functionally interchangable 99% of the time. It is a good distinction, though.

Mike
 
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