The new version of the AR-15 CompMag CA. Version (sold after Jan.31 2019) can accept .233, 5.56, .300ACC Blackout, and .277 Wolverine ammunition, right out of the box.
Our AK-47 CompMag will only accept 7.62x39.
The AR15 CompMag will not accept 6.5 Gendel, 6.8 SPC, .458 SOCOM, .50 Beowulf, 5.7x28mm, or 7.62x39mm.
For CompMags bought before 2019 the following applies.
The AR-15 CompMag is a single stacked design which will only accommodate .223/5.56 ammunition.
The AR15 CompMag will not accept 6.5 Gendel, 6.8 SPC, .458 SOCOM, .50 Beowulf, 5.7x28mm, or 7.62x39mm
Although this is the case, the AR-15 CompMag can be easily modified to work with .300 Blackout ammunition because the diameter of the case is the same as the .233/5.56.
Below is a picture tutorial instructing you how to do this.
How to modify the AR-15 CompMag for use with .300 Blackout ammunition.