The Best Barrel Length for 6.5 Creedmoor (With Ballistics Data)

6.5 Creedmoor is perhaps the most popular 6.5mm cartridge on the market today. It's also the most popular AR-10 caliber, replacing .308 Winchester and 7.62x51 NATO as the favorite for long-range bench shooting in the semiautomatic platform.

But to achieve optimal performance with any long-range caliber, you need to select the right barrel length. And, if you're building a tactical rifle like the AR, you probably want to compromise on barrel length by picking the shortest possible barrel that provides the most performance.

So, what is the best barrel length for 6.5 Creedmoor? Here's the ballistic data with the answers.

6.5 Creedmoor Barrel Length vs. Velocity Chart

Data courtesy of Rifle Shooter Magazine

The above chart shows the 6.5 Creedmoor's muzzle velocities at different barrel lengths for two of the most popular loads: 120-grain Hornady A-MAX, and 142-grain Fiocchi Sierra MatchKing HPBT.

Muzzle velocities were measured at in 16" barrels and up to 27" barrels. Every one-inch increase in barrel length shows the gain in additional muzzle velocity for both loads. The velocities at each length were captured by finding the average feet per second (FPS) using 5-shot groups. The standard deviation illustrates the minimum and maximum velocities captured at each barrel length.

For example: The 120-grain A-MAX load produced an average of 2,728 FPS in a 16" barrel, with a standard deviation of approximately 22 FPS. So, the range of velocities measured at 16" was 2,706 to 2,750 FPS.

18" to 20" is The Best Barrel Length for Building a Compact Rifle

The 120-grain A-MAX produces 2,819 FPS with a 20" barrel, obtaining 95% of cartridge's advertised muzzle velocity (2,910 FPS, according to Hornady).

The 142-grain SMK produces 2,562 FPS with an 18" barrel, obtaining 95% of the cartridge's advertised muzzle velocity (2,675 FPS, according to Fiocchi).

Want to build an AR-10 in 6.5 Creedmoor with an 18" to 20" barrel? We've got you covered: Grab one of our 6.5 CM build kits!

22" is The Maximum Effective Barrel Length for 6.5 Creedmoor

If you want to maximize 6.5 Creedmoor's accuracy using the shortest possible barrel, 22" is the length you should choose. With a 22" barrel, you'll achieve 99% of advertised muzzle velocities for both loads:

• 120-grain A-MAX: (2,872 / 2,910) * 100 = 98.69%
• 142-grain SMK: (2,649 / 2,675) * 100 = 99.02%

A 24" Barrel Isn't Necessary for 6.5 Creedmoor

6.5 Creedmoor produecs greater-than-advertised muzzle velocities when fired from a 24" barrel. The 120-grain A-MAX achieves 2,918 FPS; that's 10 more FPS than the advertised 2,910 FPS. The 142-grain SMK produces 2,683 FPS; that's 8 more FPS than the adverised 2,675 FPS.

Increasing barrel length to 24" and beyond can even result in a loss of muzzle velocity. The ballistics data shows that 142-grain loads lose 4 FPS of muzzle velocity in a 25" barrel vs. a 24" barrel, and 120-grain loads have such a wide standard deviation at 25" (45.8 FPS) that they, too, can produce muzzle velocities below what is yielded with a 24" barrel.