July 14th 2023You can choose between a 35gr varmint and a 90gr match bullet in.224 caliber. You must also consider MV along with bullet design and length when choosing twist rate. The initial spin rate of a bullet (RPM) depends on the muzzle velocity of the bullet and the spin imparted to the barrel by the rifling. You want your bullet to remain stable during flight. Many ballistics experts, such as Bryan Litz from Applied Ballistics, believe that it is better to have more spin than not enough. Glen Zediker, who died in 2007, provided some basic tips on barrel twist rates and bullet stabilty. These tips are from Glen Zediker’s book Top Grade Ammo.
I’d rather have a twist that is too fast than one that is not fast enough. Generally… I recommend going with the faster option when making a decision about a barrel-twist. 1:8? Twist is now the “new standard” in.224 caliber and replaces 1:9? In the process, 1:9? New bullets are bigger than older ones. Don’t let too-slow barrel twist rates limit your ability to [achieve] improved long-range performance. Base your next barrel-twist rate decision on your choice of the longest and heaviest bullets. If you are going to shoot a 55-grain,.224 bullet, then there is no reason to not use a 1:12?. A 1:10? is also appropriate for.308 caliber, unless you are going over 200 grains. The bullet length is more important than weight
Bullet length and not weight [determines] how much rotation you need for stability. Twist rate recommendations are usually made based on bullet weight. However, this is more for convenience. The reason is that with the introduction of higher-ballistic-coefficient bullet designs, which are longer than conventional forms, it is easily possible to have two same-weight bullets that won’t both stabilize from the same twist rate.Evidence of Instability
The tell-tale for an unstable (wobbling or tumbling) bullet is an oblong hole in the target paper, a “keyhole,” and that means the bullet contacted the target at some attitude other than nose-first.Increasing Barrel Length Can Deliver More Velocity, But That May Still Not Provide Enough Stability if the Twist Rate Is Too SlowBullet speed and barrel length have an influence on bullet stability, and a higher muzzle velocity through a longer tube will bring on more effect from the twist, but it’s a little too edgy if a particular bullet stabilizes only when running maximum velocity.My failed 90-grain .224 experiment is a good example of that: I could get them asleep in a 1:7? I could get them to sleep in a 1:7 twist, 25-inch barrel that was chambered in the.22 PPC but not in a 20 inch 1:7? .223 Rem. These tips were adapted by Glen from his popular 2016 book Top-Grade Ammo. It is now available on Amazon for $38.95. This book contains many articles on technical subjects. Here are links to other books by Glen Zediker.
Similar Posts:Tags: .223 Rem, AR 15 Book, Barrel Rifling, Glen Zediker, Midsouth Shooters Supply, Top-Grade Ammo, Twist Rate
