300 Blackout test, as promised

BenL · May 22, 2011

In a previous thread, I posted that I picked up a 300 Blackout upper and said that I would post results when I had them.

I went to Hap Baker yesterday, and put 80 rounds down range to test the new upper. I shot 20 rounds, then started recording velocities for the upper. I was shooting factory Remington 220gr subsonic ammo.

The gun was set up with a 16" CMMG 300 AAC Blackout upper with 51T suppressor quick attach, Rock River National Match trigger, Magpul PRS stock, American Defense base and U.S. Optics 1.8-10X scope.

My question was one of accuracy: is this upper a 1 MoA upper? The answer is "probably". In the end, I think the limiting factor was the factory ammo.

After shooting and measuring 30 rounds, the average speed was 1062fps, with a standard deviation of 44.1fps and an extreme spread of 186fps (1010 and 1196.) At the end of the 80 rounds, I could look at the speed and call how far off the shot would be. If the rounds were consistent, I would get 100 yard groups like this (yes, I'm aware it's only a 3 shot group):

However, it was tough getting a few rounds that were (nearly) the same speed, so most groups looked something like this:

If you look close, you can see the two top holes look as if the bullet went in a little canted; like the bullet didn't quite stabilize.

I'd bet with hand loading, I could get consistent 1" groups, if I do my part.

Jimbob2.0 · May 22, 2011

What is the advantage of blackout without a suppressor

Kingjamez · May 22, 2011

Thanks for the write up. That's pretty poor consistency from Remington. I wonder if it a sign of the newness of the production line. It looks though that the round itself if loaded properly could be as accurate as you want it to be.

I'm a bit surprised that your 16" barrel didn't go supersonic. They must have a super fast (pistol?) powder since the 9" barrels seem to have similar velocities.

Have you got any of the supersonic blackout to test?

Jimbob: I think this was just a test and he removed as many variables as possible to attian consisten results. Im sure under normal shooting he'll have that nice rifle suppressed.

-Jim

Kingjamez · May 22, 2011

Oh, I forgot to ask: Was your paper supported from the rear? If not, the odd shaped holes could have been from the lower velocity of the rounds tearing more than punching through the paper. I've had that happen to me upon shooting sub-sonic rounds.

-Jim

BenL · May 22, 2011

Jimbob2.0 said:
What is the advantage of blackout without a suppressor

It can push a 123gr bullet ~~2150fps~~ 2300fps to hunt and, in the same barrel, push a subsonic 220gr 1050, that will still be traveling 950fps at 300 yards, retains more energy than a 45ACP at point blank range.

As for why I was shooting subsonic rounds without a can, the BATFE says I can't have it for ~three months. (I have purchased, but cannot yet receive, an AAC 762SD)

BenL · May 22, 2011

Kingjamez said:
Thanks for the write up. That's pretty poor consistency from Remington. I wonder if it a sign of the newness of the production line. It looks though that the round itself if loaded properly could be as accurate as you want it to be.

I'm a bit surprised that your 16" barrel didn't go supersonic. They must have a super fast (pistol?) powder since the 9" barrels seem to have similar velocities.

Have you got any of the supersonic blackout to test?

Jimbob: I think this was just a test and he removed as many variables as possible to attian consisten results. Im sure under normal shooting he'll have that nice rifle suppressed.

-Jim

The factory ammo was designed around the 16" barrel. The upper has an interesting construction; the gas block looks like a pistol gas system. It's set far back in the upper. Yeah, for the price of the ammo, I was a little surprised at how poor the performance was, as well.

I didn't have any of the supersonic ammo to test. My interest is in the subsonic longer range possibilities. (I'm waiting on a can...)

Jimbob2.0 · May 22, 2011

Thanks in was more curious since it seems like a neat caliber with a lot. Of potential

Kingjamez said:
Thanks for the write up. That's pretty poor consistency from Remington. I wonder if it a sign of the newness of the production line. It looks though that the round itself if loaded properly could be as accurate as you want it to be.

I'm a bit surprised that your 16" barrel didn't go supersonic. They must have a super fast (pistol?) powder since the 9" barrels seem to have similar velocities.

Have you got any of the supersonic blackout to test?

Jimbob: I think this was just a test and he removed as many variables as possible to attian consisten results. Im sure under normal shooting he'll have that nice rifle suppressed.

-Jim

BenL · May 22, 2011

Kingjamez said:
Oh, I forgot to ask: Was your paper supported from the rear? If not, the odd shaped holes could have been from the lower velocity of the rounds tearing more than punching through the paper. I've had that happen to me upon shooting sub-sonic rounds.

-Jim

It's stapled to the plastic backing that's at Hap.

Russ D · May 22, 2011

Ben what is your opinion of the CMMG upper and what did it cost you? I may go this route instead of building my own if you get good results from yours.

BenL · May 22, 2011

Russ D said:
Ben what is your opinion of the CMMG upper and what did it cost you? I may go this route instead of building my own if you get good results from yours.

It was $659, free-floated, and is surprisingly well-made (it didn't come with the suppressor adapter; that was extra.) They also make one without rails that is ~$80 less. It's got a pistol length gas system, so can easily be cut down, if desired later.

I was originally going to build my own with a Noveske barrel, upper, and lower, but for the cost, I thought I'd try a cheaper alternative, first, to see what I think of the caliber.

The 220gr recoil is unusual; it's more of a light "push" than recoil. You can easily stay on target, similar to a .22LR.

VWTurbo · May 22, 2011

Great review. thanks for the info

rsilvers · May 23, 2011

123 grain bullets can go about 2300 fps from a 16 inch barrel.

The velocity spread is due to the nature of loading subsonic rifle ammo that will cycle a 300 AAC BLACKOUT AR, not due to manufacturing.

Kingjamez · May 23, 2011

rsilvers said:
123 grain bullets can go about 2300 fps from a 16 inch barrel.

The velocity spread is due to the nature of loading subsonic rifle ammo that will cycle a 300 AAC BLACKOUT AR, not due to manufacturing.

Care to elaborate? Are you implying that hand loading will not solve the velocity problems?

-Jim

BenL · May 23, 2011

rsilvers said:
The velocity spread is due to the nature of loading subsonic rifle ammo that will cycle a 300 AAC BLACKOUT AR, not due to manufacturing.

I thought of this, as well. That being said, I have yet to shoot factory ammo that wasn't improved on when hand loading specifically for the rifle. I picked up some Forester dies; as soon as I find some AA1680, I'm going to reload some and see how it goes.

rsilvers · May 23, 2011

Yes. I pulled 20 bullets from the Rem ammo and all charges were +- 0.1 grains. Or maybe it was +- 0.2 for 1 or 2 rounds. I don't have my notes. In any case, it was a good result. The velocity spread can be improved with faster powder, such as N110, but the the guns would need larger gas ports and cease to be able to shoot full power ammo. We (I worked on it) decided functional reliability was most important and the accuracy with subsonic was still 2 to 3 times better than the MP5-SD we see as the competition. So to further improve accuracy at the expense of reliability did not seem like a good idea.

If you mix subsonic and full power ammo, the cases eject to about the same spot - which is great. Even different brands of 223 vs 5.56mm don't do that.

I plan to develop dedicated subsonic bolt action ammo which should have less velocity spread.

BenL · May 23, 2011

rsilvers- Do you have a lot of experience with this round? If so, would a 10" barrel deliver (pretty much) the same accuracy as the 16"?

ETA: OK, I see you're the project lead. Awesome. You're the guy to ask.

SCARCQB · May 23, 2011

How quiet is It????????

This has gotten me more excited than the rapture thing.

Cerebus · May 23, 2011

BenL said:
rsilvers- Do you have a lot of experience with this round?

He should.

BenL · May 23, 2011

SCARCQB said:
How quiet is It????????

This has gotten me more excited than the rapture thing.

Actually, even without the can, it's pretty quiet (maybe a little louder than a CCI minimag?). I can't wait to get the can.

I hate waiting.

SCARCQB · May 23, 2011

I just got a 300 blackout barrel from CMMG. I 'm having it cut down to 9", threaded 1/2x28tpi. Dedicated for subsonics and planning to mount a 9mm can ( 1.375") under the handguards.

BTW... any issues with keyholing?

300 Blackout test, as promised

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