I just found a goofy little cartridge case at the range. It was obviously made on cut down LC 5.56 brass. I have identified it as .300 Blackout. My first thought was "What a stupid idea!" but after researching it I'm starting to think it's kind of charming. Does anybody have any real life chrono figures for bullets from 110 to 150 grs.? It is alleged to be faster than the 7.62x39 but I don't see how that's possible, given the obviously smaller case capacity. Would it be necessary to inside neck ream the 5.56 brass after cutting it down?

Dave Sinko

I do not know what the blackout does, but it will also shoot 300 Whisper. You can load a Whisper with a 220 grain subsonic that suppressed you could not hear in the other room or a 125 gr at 2400 fps. It's a versatile cartridge. Especially for SWAT or Spec Ops....

It can be used off of existing AR platforms, load the same number of rounds as the .223, same mags etc., just a barrel change.

Found this on the .300 Blackout

Maximum effective range =

460 metres (503 yd) 125 grain supersonic
200 metres (219 yd) 220 grain subsonic

Barrel Cartridge Velocity Energy
9 in (230 mm) barrel 300 AAC Blackout, 115 gr UMC 2,120 ft/s (650 m/s) 1,136 ft·lbf (1,540 J)
16 in (410 mm) barrel 300 AAC Blackout, 115 gr UMC 2,295 ft/s (700 m/s) 1,344 ft·lbf (1,822 J)
9 in (230 mm) barrel 300 AAC Blackout, 125 gr OTM 2,030 ft/s (620 m/s) 1,143 ft·lbf (1,550 J)
16 in (410 mm) barrel 300 AAC Blackout, 125 gr OTM 2,215 ft/s (675 m/s) 1,360 ft·lbf (1,840 J)

The 300 AAC Blackout cartridge IS a 300 Whisper as designed by JD Jones. The Only difference is the chamber which has slightly longer throat. It was originally based on a 221 Fireball necked up to 30cal.

Hodgdon's 2012 Annual Reloading Manual (magazine) has a decent write up about it. It's a nifty little cartridge suitable for the AR platform but designed for specific needs as well.

I was doing some research on the 300 Blackout this week and found some interesting information on this link. He has several videos, including information on how to make the rounds, test session with Advance Armament with data etc, pretty neat.

Ammunition Review: .300 AAC Blackout | The Truth About Guns

Is there a quicker way to trim all that brass? Is there such a thing as a hardened steel trim die that allows the use of a hacksaw? Would that speed things up or cause even more fatigue? And I mean fatigue to the user, not the cartridge case. This seems very labor intensive outside anything other than a small scale operation.

Dave Sinko

Not sure if a trim die exists but I agree it does seem labor intensive. An electric bandsaw or dremel tool might be the trick to get the brass in the ballpark for a final trim? I did find someone processing the brass and offering it for sale.

Buy Brass * BradsWarehouse.com - Custom made 300 AAC Blackout Brass

Here's another source:

http://www.allweatherarms.com/1000-P...0-Blackout.htm

I presume .223 brass is just as good? Once you cut these cases below the shoulder is there any difference between .223 and 5.56 to matter?

Does anybody know if the 110 gr. RN meant for the .30 Carbine will feed in .300 Blackout rifles?

Dave Sinko

The 115gr spec looks a lot like a .30 Carbine, I guess whats old is new again, just like recycled songs.

Trim it off in a lathe.

Someone (don't remember who) makes a cutoff die. Same type used to cut off 308/30-06 to make 44 Automag brass. Insert the case, run it up to full press, and cut off with hacksaw or Dremel.

Yes another HO-HUM cartridge. 7.62x39 handloaded will do anything it will do better.....Bigger case/more horsepower.

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S&W Accumulator

I tend to agree the 7.62 x 39 may do some things better. However, not on an AR platform. The advantage here in my eyes is the 300 ACC can run on existing AR rifles via either changing the entire upper or just the barrel all the while using your current mags. Plus, in a SBR set up with a muffler and subsonic rounds it does well compared to lighter caliber rifles and can become a longer range rifle by changing out a mag with different ammo.

Lots of 7.62x39 AR uppers available and if you download from full capacity the 5.56 clips they will usually work the the AK round.
Don't see it as a long range cartridge......Like sending a boy to do a man's job. My $0.02.
But heck....if you like it ..buy 2.

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S&W Accumulator

Originated by AAC for their purposes. As previously mentioned 115 grain and 220 in 308 diameter. They haven't overcome the cycling problems with the AR platform and operating rods. The direct impengement(gas) method of operating the bolt works fine. In the subsonic mode it may the ideal basement rat killer. Even better with a surpressor. I'm still investigating the possibilities.

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... fortunate son...