Will a .308 Muzzle Brake work on a 6.5 Creedmoor?

Will a .308 Muzzle Brake work on a 6.5 Creedmoor? Does the internal diameter of a muzzle brake effect recoil reduction? This is a very common question, derived from the desire to purchase only one muzzle brake to use for multiple caliber sizes. American Precision Arms’ R&D department set out to find the answer to this mystery.

Common sense would tell us “of course it matters.” The reason for this revolves around the way a muzzle brake works.  The purpose of a muzzle brake is to reduce recoil by redirecting the gas that is otherwise propelled forward. If all the gas is going forward, the gun is propelled backward into the shooter.  By installing a muzzle brake, we hope to peel off as much gas as possible from the forward gas stream rendering the rearward propulsion less aggressive. Based on this well-accepted theory, one would assume that a larger internal diameter of the muzzle brake would allow more gas through as the projectile is passing through it, rendering the muzzle brake less effective.  

The Testing Equipment

 APA wanted to be certain that this was the case and if so, how much reduction does the smaller caliber lose by using a muzzle brake for a larger caliber? Using Cal Zant’s recoil testing fixture with an impulse data reader, APA was able to get some concise answers and the results were not quite as expected. In addition to Mr. Zant’s device, we used an APA Genesis rifle chambered in 6.5 Creedmoor with a Broughton Sendero contour barrel and Manners TF1 stock. Overall, the rifle weighed about 11 pounds without optics. The muzzle brakes used were two American Precision Arms Gen 2 Little Bastards. One was a 6.5 and the other was in .308.

(NOTE: APA bores their muzzle brakes at .032” over bullet diameter for safe, consistent projectile pass-through. The 6.5 muzzle brake’s internal diameter is .296” and the .308 muzzle brake’s internal diameter is .340”)

The Surprising Results

 Though a consistent difference in recoil reduction was detected, it was constantly very small. The 6.5 Gen 2 Little Bastard muzzle brake performed between 1-3% better than the 30 caliber muzzle brake. We then decided to move this test to the bench with a handful of fairly avid shooters to further investigate if this 1-3% could be felt. We did add an optic to this portion of the test. An almost unanimous verdict surfaced. All but one shooter claimed they could not feel a difference between the two brakes, while the lone wolf said there was a slight exaggeration in crosshair movement when utilizing the .308 muzzle brake.

The Big Question

So, should you buy one brake to cover multiple calibers or keep your brakes caliber-specific? Well, this really depends on how serious of a shooter you are. Is the muzzle brake purchase simply to tame the recoil? Is being cost-efficient a high priority? Or is this for competitions like the Precision Rifle Series, where every iota of detail adds up on the scorecard at the end of the day? Is that 1-3% going to scratch at the back of your brain? That’s a decision you are going to have to make all on your own.