Best Bullet Grains For 1 In 7 Twist
Hornady 75 grain bullets usually shoot well from 1/9, but some rifles won't shoot them for shit. 75's and 77's are your go to for magazine fed bullets and longer range shots. The 1/7 will stabilize them for sure. 55 grain and 62 grain FMJ's are perhaps the lowest quality bullets available. What grain bullet is best for a 1:7 twist barrel? :?: After a long absence, I want to get back into EIC and service rifle competition. I have a Colt Sporter Match Heavy Barrel in 5.56 mm of course, and according to what I remember it is a 1:7 twist barrel. What grain bullet have you guys found has the best accuracy out of a 1 in 7 twist 5.56 barrel? I wouldnt mind having some good load info also but its pretty hit or miss what they have in stock for powder around here right now.
Higher number twist rates perform better with lighter grain bullets, while lower number twist rates perform better with heavier grain bullets. Common wisdom for 5.56 NATO and .223 Rem. indicates those barrels with a rate of rifling at 1:9 or slower (1:10 etc.), in general, perform best with lighter bullets—60 grains or less. My personal AR with 1 in 7 twist does best with bullets 69gr and up. The 55 and 62 gr usually have groups twice as large. Paranoia is more than a personality trait, it's a survival skill. 06-04-16, 16:11 #3 you should have no problems with any bullets from around 50 grains and up. i think a pretty good rule of thumb is 1/7 for bullets of 50 grains and up, and for 1/9 70 grains or less. FlyinBryan, Sep 19, 2011 #2 I always buy 1-8 twist barrels they will stabilize 75-77 bullets no problem no matter the barrel length, which are the heaviest bullets that can be magazine length loaded. 223 can't be loaded hot enough to get even very lite bullets 35gr to come apart so really there is no downside to going with the 1-7 twist in 223 and you can shoot any bullet weight.
Using them will allow you to estimate the heaviest/longest bullet a gun will stabilize based on the caliber (left-most column) and twist rate in inches (top-most row). For example, a 45 (.457) caliber rifle with a twist rate of 1 in 18″, should be able to stabilize a bullet up to 672 grains or 1.74″ in length. Twist rate is measured in inches and displayed as a ratio of 1 revolution per "X" number of inches. For example, the rifling of a barrel with a 1:7 (1/7, 1-7, 1 in 7, etc.) twist rate makes a full revolution every 7 inches. The best twist rate for a given bullet is determined based on the projectile's length, diameter, and weight. After testing settled on 66.8 grains of Reloader 26 with a MV of 3088. Did a water jug test yesterday @ 250 yards. Great expansion and 111 grains of bullet left intact. If you are shooting farther and want a higher bc you could experiment with the Accubond LR. Won't know until fall how the bullet works on deer size game. My
Another example is current issue 5.56mm M856 tracer ammo. That round weighs in at 63.5 grains and requires a 1:7 twist to properly stabilize, because it's so long A typical length .224 bullet @ 63.5 grains would stabilize just fine out of a 1:11. I myself, have shot M856 out of a 1:9 Bushy and had keyhole strikes at 25 yards. 1-in-10 Inches Twist Rate. My first centerfire rifle was a Ruger Mini-14 with a 1-in-10 twist. This is a good twist rate for lighter bullets and will also generally stabilize projectiles up to 69 grains, such as Federal Premium's Sierra MatchKing BTHP load. If you're happy with 55- and 62-grain FMJ bullets, you don't need any more twist than this. As we get faster and faster twist rates - this is becoming more of an issue. I personally know a few guys with 1:7.5 Creedmoors that are having the Hornady Match projectiles spinning their jackets off on them mid-air. Twist rates and bullet weight are often understood, but there are some simple and practical guidelines.
Barrel Twist How many "inches per turn" is your rate of rifling twist. This number is used along with other inputs to determine the stability and related trajectory metrics. Typical value for this input is between 1:7" and 1:13". It does not require a heavy bullet but heavy bullets require a 1/7 or a 1/8 twist. I shoot 77 grain bullets in my 1/7 and 1/8 guns for matches and accuracy work. I use 55 grain ball for plinking. I know the AR556 has a 1/8 barrel twist rate and that will help stabilize larger weight bullets, but to what extent. I was reading an article about a 77 grain bullet that recommended a barrel with a 1/7 twist, so it got me wondering what bullet weights are ideally suited for the 1/8 twist the Ruger has.
Lastly, the 1:7 twist barrel is the "mil-spec" choice, as the U.S. military adopted this setup in the 1980s for its M16A2 rifle running a 62-grain M855 5.56 round. The 1:7 barrel, found in the M4, M16A4, Mk12 SPR and HK416, can stabilize up to a 90-grain bullet, and handles 70- to 77-grain projectiles across a wide spectrum of velocities. 7.62x51 went to the 147 grain bullet. That was the standard for use out of the 24" 1/10 Garand and Springfield 03 barrels. It was and the marksmen of the era made sure to test ammo and put aside good lots that performed in their rifles. The early M16A1 utilized a rifle twist rate of 1:12 to stabilize the 55 grain M193. After the adoption of the M16A2, the military started using a 1:7 rifle twist, which was faster. The rifling made a complete revolution within 7″ now instead of 14." We are talking twice as fast.