CMMG .300 BLK Rifles

CMMG AR15 300BLKI may be the last person to have heard, but CMMG is making AR-style rifles chambered for the .300 BLK cartridge.  (As it turns out, I was not.  I got an e-mail from a guy who had been stranded in the arctic for the past six months who had not heard about these rifles either.)

Essentially, there are four variants of the M300 Blackout rifle.  All four of the carbines have 16″ barrels with 1:8 twist and a six position M-4 style buttstock.  Two of the models have a flat top receiver, no sights and a mid-length quad-rail.

The other two CMMG M300 versions have the flat top receiver, A2 front sight, Magpul rear BUIS and the standard carbine length handguard (no rails).

Both versions can be had with a pistol gas system or a carbine gas system.  According to the CMMG materials, the pistol length works best with unsuppressed subsonic ammo but is also acceptable for suppressed subsonic ammo.   CMMG does not recommend the use of supersonic ammunition in the pistol gas systems.

The carbine length gas system is recommended by CMMG for suppressed sub- and super- sonic ammunition plus suppressed subsonic ammo.  It is deemed acceptable for unsuppressed subsonic ammunition.  There is a whole lot of thinking that seems to be needed for the purchase of the correct rifle for your needs.


All rifles ship with a 30 round magazine.  Prices range from $899.95 to $949.95.  Generally, these retail prices are not too bad.  I’ve seen a lot of .300 AAC Blackout rifles selling for more than $1,100.  So grabbing one for $950-ish sounds like a pretty good bargain.

As I have noted before, there are a lot of products being made for the .300 BLK cartridge.  I strongly thinking about picking up either an upper or a whole new gun for this cartridge.  What do you guys think?

CMMG M300 300BLK


By Richard Johnson

Richard Johnson is a gun writer, amateur historian and - most importantly - a dad. He's done a lot of silly things in his life, but quitting police work to follow his passion of writing about guns was one of the smartest things he ever did. He founded this site and continues to manage its operation.

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