Matching twist rate and bullet weight in rifles.

HomeContentBallisticsMatching twist rate and bullet weight in rifles.

The are many benefits to understanding and matching the twist rate of your barrel with the projectile weight you are using. Primarily, accuracy. This article is a high-level overview of the subject, and as such, a few concepts and terms are simplified. If you want a truly in-depth study of the subject – get Brian Litz’s series of books from Applied Ballistics. If you want functional information, read on.

Too fast a twist rate and the projectile can potentially damage the projectile jacket as the excessive force separates the jacket from the core. 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.

But first, a little background.

TWIST RATE

You can read an expanded article on twist rate over here – but in summary, a twist rate is the number of times your rifling (the groove in your firearm barrel) makes a full revolution over a set distance – this is generally expressed in inches – so a “1 in 10” makes one revolution of rifling every ten inches of barrel length.

BULLET WEIGHT

Bullet weight has increased as we are reached out further and further with our rifles.

A heavier projectile (more grains) will often come with a better (higher BC) – that is, the ability of the projectile to buck wind – they fly truer, for longer.

bullet weight, Matching twist rate and bullet weight in rifles.

However, it’s not just as simple as putting the heaviest bullet you can down the barrel. More weight requires more powder to move – and speed is still a priority as a slow-moving bullet spends more time in the air, has more time to be affected by the wind, and in the understanding that everything drops at the same speed (thanks, gravity!) the faster it moves, the further it can reach with less ballistic drop.

MATCHING TWIST RATES AND BULLET WEIGHT

So, in very simple terms, the heavier the projectile (it is actually a function of bullet length and sectional density, but we are simplifying things here), the faster (lower number) twist rate you are likely to want to utilise.

I know, I know, just tell us already – what do I put in my rifle?

Well – here is a very basic chart that will set you off on the right foot. Like all things reloading, there are always exceptions.

Twist RateProjectile Weight
.224 / 5.56 (your .223 Ar)
1:16Up to 55 grains, 4300 fps or more
1:15Up to 55 grains, 4100 to 4300 fps
1:14Up to 55 grains, less than 4100 fps
1:1255-63 grains
1:963-70 grains
1:870 grains or more
6.5mm
1:9Up to 130 grains
1:8130 grains or more
.308
1:15up to 150 grains
1:14150 to 168 grains
1:12168 to 170 grains
1:10170 to 220 grains
1:8220 grains or more

This is just a quick list to give you an idea.

But wait… There’s more!

Want to get the rest of the article? Then simply join up as a member and gain access to all the extra content here and over on The Bloke!

For around the cost of a cup of coffee per month (in Auckland, I do admit) you support the projects, get extra content and become an all-around good bloke.

Click the button, join up, then refresh this page here to get all the extra content!

In this article – seven simple steps you can take to start reducing your ES/SD right now!

OVERSTABILISING THE ELD-M PROJECTILE.

I recently have had a good mate who has been destroying ELD-M’s with abondon.

It’s a 1:7.5 Twist, chambered for 6.5 PRC and he is getting projectiles disintegrating mid-flight. Too be fair – he is running right at the ragged edge of velocity/pressure/speed and the resulting twist these things are undergoing – but – it’s not super crazy what he is doing.

If you have a projectile that just seems to be going a little crazy – or – even missing rounds on target – it might be worth considering if we have managed to out twist some of the options on the market.

 
Kerry Adamshttps://thebloke.co.nz
A constant learner with an inquisitive mind, Kerry created The Bloke as a way to share what he was learning from the community of experts he found himself surrounded by. Precision Shooter and GunSafe soon followed. Somewhere along the line, he picked up one or two things himself. But don't call him an expert.

Related Reads...

Support
Precision Shooter.

Apparently, doing honest reviews and putting together safety and education content isn't the way you become rich on the internet! So. Your support is the main, direct way to keep me doing this. Become one of the blokes to support the site and related projects. Good on ya mate!