.300 BLK Range Report

[uvausmc]

Just got done test firing my new .300 AAC Blackout build.

The rifle started off as a basic M1S carbine upper on a Stag lower. Over the years I had fixed it up with Magpul CTR stock, MIAD grip, MI extended forearm and optics. I've been reading a ton about the .300 BLK and have a few 5.56 AR's so I decided to convert one.

I changed the barrel to a CMMG .300 BLK 16" barrel with an AAC Blackout Muzzle Brake. I also switched to a YHM flip up front sight gas block. The rifle turned out great! Function was flawless with Remington 115gr FMJ ammo. all brass landed about 6 feet away at 4 o'clock in a nice neat little pile. Recoil was like shooting 5.56 and the muzzle blast was not any noticeably louder.

I also shot some handloads with 110gr Hornady SP over 15.1 gr of 2400 but these were too light. They would chamber, fire, and eject fine but did not push the bolt back far enough to pick up the next round. I'm going to bump up the charge and try again but they should result in a great inexpensive plinking load.

The factory load chrono'd and average of about 2200 fps and the handloads were just over 2060 fps. I didnt shoot for groups but accuracy off hand was a few inches at 50 yds with the dot sight.

Now I just need to get my AAC 7.62-SD and the setup will be complete.

Total cost of the project was $350 for the parts and was definitely worth it.

 

[Coltdriver]

Looks nice! And for what you are shooting they are very light in recoil.

Did you happen to measure the gas port size on the barrel. I am just curious.

I built a 300 BLK and found the gas port has to be about .110 to get the bolt to cycle correctly.

My 125 and 130 grain supersonics cycle great and lock back the bolt on last round. My 220 grain sub sonics cycle great but do not lock back the bolt on last round.

I think the only downside is you can blow through a lot of 30 caliber bullets in a very short time!

 

[uvausmc]

I didn't measure the gas port. Eyeballing it, it looked like the same size that was on my 5.56 factory barrel I took off. I'm pretty sure the cycling issue was due to the light handloads since the factory ammo cycled no problem.

 

[helotaxi]

I finally got my BLK to the range today as well. Upper is a YHM with a Wilson Combat 16" fluted barrel and a Cooley brake and a YHM rifle length rail. The lower is a YHM with a MOE grip and stock. It currently wears a Vortex Strikefire. Shooting reloads with pulled 147gn Winchester FMJs and AA1680, I got it sighted in at 25yds. The confirmatory 5-shot group was a single ragged hole. Moved out to 100yds and got a hand sized 10-shot group. Considering the lack of load development and the crappy bullets, not to mention that I was using a 4 MOA red dot, I'm happy with that for now. I'll get ahold of some good bullets at some point and see what it can do.

Between the round and the brake, recoil is non-existent. The dot didn't move appreciably with each round fired. It's a good thing I'm working with cheap pulled bullets cause this thing is silly fun to shoot. Like a loud .22 that makes a big hole. Now that I've shot it, I like it enough to keep it. I'll form some more brass tonight and tomorrow.