Many shooters measure the quality of their rifle by the size of the groups it shoots. While there is way more to rifle quality than just that, understanding why a bolt action rifle is inherently more precise than a semi automatic rifle (on average) will help shooters understand the sport a little better.

So why are bolt actions more precise?

Bolt action rifles shoot smaller groups for one major reason: They shoot more consistent bullet velocities. Why that is we’ll explain later.

When shooting long distances understanding why bullet velocity matters is easy. If a bullet is traveling 100 fps faster than the last shot, gravity won’t be able to affect it as much and you’ll end up with a greater vertical spread. BUT, this doesn’t explain why, even at shorter distances, you end up with larger groups.

So what’s happening here?

This comes down to something called Barrel Harmonics. As I’m not an engineer I won’t make myself sound stupid by over explaining, but THIS does an excellent job of going into more detail. If you don’t want to read that whole article have no fear. All you need to know is, when fired, your barrel vibrates very quickly and moves much like a wave.

Now we’ve got to the crux of the problem. Bullets leaving the barrel at different speeds, will also leave at slightly different points in that wave, dispersing your bullets. Simply put you’ll end up with a bigger group.

Here’s a few things you can do to improve Barrel Harmonics

• Make your barrel Shorter or Girthier or both. Shorter and thicker (bull) barrels will be stiffer reducing movement.*
• DON’T use a Barrel Tuner. Tuners are small weights that can be attached to your barrel to control and tweak the harmonics. As of writing this there isn’t any real evidence to prove these work. That won’t stop you from seeing these advertised all over the place though! I’ll add a caveat here, shooting happens at incredible speeds and I’d be happy to one day be shown that these things actually work. Until then I wouldn’t touch them.
• Free Float your barrel. Make sure your barrel isn’t in contact with anything that could hinder or change it’s movement.
• Reload or buy match grade ammunition to reduce velocity deviations.

*Carbon fiber barrels often claim to make your barrels stiffer but this isn’t true. They will make your barrel stiffer at the same weight. However, carbon fiber barrels are wayyyyy lighter than their steel counterparts.

Why are bolt action rifles more consistent with their velocity?

When talking about semi automatic rifles, we’re more specifically referring to something called gas impingement and gas piston systems. These make up the vast majority of all semi automatic rifles.

While this system can be highly reliable it just can’t be as consistent as a bolt action. Small variations in the quantity of gases that escape are inevitable, changing your pressure and velocities. Comparing this to a bolt action, that expels all it’s gases out the muzzle, it’s inevitable that it can’t be as precise.

But aren’t Semi Autos more complicated and therefore more expensive?

This is 100% true.

Semi automatic rifles are significantly more complicated and therefore cost more for equivalent quality. However, this isn’t the full story.

You can find sub-MOA shooting bolt action rifles for around $500 these days, no problem. Getting your hands on a semi automatic that will, on average, shoot sub-MOA is going to cost you thousands of dollars. My MK20, a FN SCAR sniper variant I used in the military,  retails for around $5000 and I could never get that thing to consistently shoot MOA or better.

In the end, the price difference and build quality just doesn’t account for the variation in accuracy.

What’s the Takeaway?

None of this means one is better than the other. The only takeaway here is at similar price points the bolt action rifle will on average be more precise than a gas operated rifle (assuming your shit isn’t busted).

While a bolt action might be preferable in some long range scenarios or where you only get one shot. A semi automatic would likely outperform in closer rapid engagements.

At the end of the day it’s up to you to decide what you’re going to be doing with this rifle. The discussion of which is better has so many elements and variables that you should probably just own both. I know I do…

If you have any thoughts or think I missed something let me know in the comments down below and thanks for reading!