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Discussion Starter · #1 ·
Guys
I just completed a 20" AR15 project. It has a 1 in 7 twist. My last one similar to this didn't care for the light ball 55 grain ammo. What heavier ammo do these prefer? I got a box of 69 and 74 grain Privi to try. I have plenty of 55 and 63 grain range ammo as well.
 

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As mentioned it should shoot the M855 62gr fine. You can go heavy with the 1:7 at least up to 80gr. The heavy weight BTHP bullets can be loaded to fit in a magazine, for example Hornady 75gr BTHP, but OAL of non-HP in the heavy weights will exceed the size of a mag.
 

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Your lighter/shorter bullets won't be liked well but as others mentioned anything over about 62 grs should be good.
 

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Can't hurt to try 55gr ammo again in this barrel. Every barrel is a little different. To barrels that came off the MFG line one after the other will shoot different with the same ammo.... All of my AR's (1/7) shoot 55gr M193 just fine.
 

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Can't hurt to try 55gr ammo again in this barrel. Every barrel is a little different. To barrels that came off the MFG line one after the other will shoot different with the same ammo.... All of my AR's (1/7) shoot 55gr M193 just fine.
^This^ I've got uppers with 14.5" barrel with 7" twist, 23" stainless bull match barrel with 8" twist, and 16" carbine length barrel with 9" twist. It is my belief that the higher the twist rate the longer and heavier bullet it is able to stabilize. Just because a barrel will stabilize heavier rounds doesn't necessarily mean they will be the most accurate.

I agree with cms81586, your 7" twist will stabilize the heavier grains but don't be afraid to try some lighter ammo, even varmint loads.

Case in point: My friend Bob has a 20" stainless bull match barrel with a 8' twist. The gun shot O.K., but Bob wasn't happy with the group sizes. After trail and error, he came up with a load of AA 2015 on a 50g V-max bullet and the gun became a tack-driver. I watched him shoot three 5-shot one-hole groups @ 100m. The groups were so tight that they didn't appear clover-leafed, just one hole with the edges only slightly expanded! (Bob is a helluva shot also)
 

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Discussion Starter · #8 ·
Thanks guys
I plan to op check it and do the basic sight in with 55 grain. Then I'll try the 62. 74 and 76 grain stuff to see how it prints.
 

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Can't hurt to try 55gr ammo again in this barrel. Every barrel is a little different. To barrels that came off the MFG line one after the other will shoot different with the same ammo.... All of my AR's (1/7) shoot 55gr M193 just fine.
Agreed, you need to find out what grain/type of bullet and load that your barrel likes... I bet however that at 100 yds youll be better off with a 69gr rather than 75+. I guess youll find out soon!
 
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