selecting barrel length Archives

Preface

If you find yourself rebarreling a rifle, be it as an upgrade or because it has been worn out, you might be asking yourself a few questions. Today we are going to discuss how to pick the right barrel length and twist rate. Barrel length has a lot to do with performance, and the twist rate inside dictates the bullets you can shoot through it. In our discussion today I hope to illuminate how these topics should be approached and evaluated.

Ruger American Gen 2, Maven Optics, — Modern rifles are trending towards faster twist rates and barrel lengths to match. **This Ruger American gen 2 rifle** is paired additionally with a **Banish Suppressor** and **Maven riflescope**

Barrel Length

The length of your barrel has a great deal to do with velocity. Typically, longer barrels produce higher velocities all else being equal. A 308 Winchester loaded with 165 grain bullets would likely have a muzzle velocity around 2800 FPS. When you look at test data they usually post the barrel length they used to get that velocity (often a 24-26 inch). So if you have an eighteen-inch barrel on your 308, you are likely going to get a much slower muzzle velocity when using the same 165 grain load.

Various studies have been done showing velocity reductions as barrels are cut down. With most cartridges it seems the drop in velocities become greater past a certain length. For example, cutting from 26 to 24-inch you may only lose 25-50 FPS. But cutting a 20 down to 16-inches, the loss will be much greater.

mant modern bullets require faster twists than previously used, like these **Hornady 180 gr 7 PRC**

This is important when making your decision, as velocity can be important depending on the purpose of your rifle. For example if you are doing long-range target shooting, you might want as much velocity as possible. While if you are assembling a short-range hunting rifle, it might be more important to have a compact rifle even at the cost of some velocity.

Burning Powder

Big magnum cartridges use a lot of powder, and the barrel length is used to allow all that powder to be burned. This is also why big cartridges use slower burning powder, so it is still burning at the end of the barrel. This keeps the bullet accelerating, whereas if the powder burns up too fast, it can be spent before the bullet leaves the muzzle.

This 20-inch **LWRC REPR** barrel allows better combustion of powder than a 16-inch version would

Ideally you’d want a long enough barrel to allow all the powder to be used to accelerate your bullet. But there are some considerations to keep in mind, sometimes long barrels are cumbersome. And its more common these days for folks to compromise between a long barrel and one that gives enough velocity without being unwieldly.

Twist Rate

In the same fashion, barrel twist is important to evaluate when deciding on your next barrel. And again for the same reasons. If you goal is shooting long-range, you will probably want to shoot high ballistic coefficient (BC) bullets that require faster barrel twist rates. Whereas if you are rebarreling your favorite varmint rifle, a slower twist rate might be optimal for the bullets you will be shooting.

antelope, pronghorn, desert tech, srs m2, us optics, — Faster moving cartridges typically use slower twists, but stepping them up to a faster twist will allow you to shoot bigger bullets faster. My **Desert Tech SRS M2** uses a variety of barrels and calibers

If you are of a certain age, you might have played with the ancient toy called a top. Often shaped similar to a bullet, you spin the top and it would stand up and spin until it slowed enough to topple over. You can imagine if a top was taller, shaped like an inverted old Coke bottle, it would be much harder to get it to spin fast enough to stay standing.