Truth about heavy grain bullets in 1:9 twist AR

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Floyd
Posts: 228
Joined: Sun Jul 09, 2017 4:11 pm

Truth about heavy grain bullets in 1:9 twist AR

Post by Floyd » Sat Dec 23, 2017 11:37 am

https://www.ammoland.com/2017/02/ar-15- ... z526qKJmeL

Seems a 1:8 twist is ideal for middle of the road bullet weight.

A 55 grain shoots fine in a 1:9 twist.

A higher grain bullet goes with lower twist barrel. 1/9 is designed for 55 to 62 grain.

One user reports his 1:9 loves 77 gr Nosler and 77 gr SMK, 1 MOA for the Nosler and about 1.5 MOA for the SMK.

So, what’s right for your AR? That depends. If I were building a strict varmint gun—something that would almost exclusively fire bullets in the 55 grain and below range—I’d opt for a 1:10 twist rate, which has proven effective for me in the past. The 1:10 is highly versatile and will work with most bullets, from 55 grain polymer tip varmint bullets on up to heavier boat-tails for a little extra reach. If I planned to shoot a bit of every type of ammunition I’d go for a 1:9 or 1:8, which would allow me to take advantage of a broad range of bullets. If I were building a long-range target gun and knew I’d be using bullets from 77 grain on up, well, I’d have a 1:7 twist.

If you are shooting long range, or want more penetration, you want a heavier bullet in the AR, such as a 62- or preferably a 77-grain. 62-grain bullets prefer a rate of twist around 1:8 and 77-grain bullets weights favor a 1:7 twist rate.

Bullet Weight: The Ideal Rate of Twist
So to simplify this for you, here is a chart you may want to print:

Bullet Weight Twist
40-Grain 1:12
55-Grain 1:9
62-Grain 1:8 or 1:7
77-Grain 1:7 or 1:8
80-Grain 1:7

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