Reloading specifics for 16” barreled AR10 in 6.5 creedmoor

[JimmyT]

I’ve built a 6.5 creedmoor AR10 with a 16” barrel. my question is about powders for the creedmoor that will be compatible with this set up. I’m currently using Hornsby brass, Sierra 130 grain game changers, br2 primers, and 42.6 grains of IMR 4451. I’m getting 2588 FPS with a SD of 9.
I also have variety and IMR 4350. I know barrel length is affecting my velocity. I’m looking for a more efficient burn in the barrel to reduce muzzle flash and maintain current velocity levels.
my thinking is leaning towards a faster powder in smaller charge weights to get a complete powder burn in the barrel. I would like to hear from any others that have more experience with the creedmoor/AR10 if this is possible and will help before I go too far down the rabbit hole.

 

[Dogtown]

Quickload estimates you're getting close to 97% burn rate in that barrel (the fps numbers don't totally match yours but are in the ballpark)

IMR 4350 is slower, so less % burn in that barrel, but pressures look safer.

Running the numbers for powders with a 97% fill rate at the pressure limits says:
- Shooters World Match Rifle & AA4064 look good but right at the edge of pressure
- RL17 won't get 100% burned but looks the most efficient in your case

 

[JimmyT]

Thank you for that information. I will stick with the IMR 4451 for now. With the 16” barrel, the rifle is very loud. I thought that was due to more powder burning outside the barrel. I’m going to a 600 yard practice shoot on Sunday to see how this rifle performs!