View Full Version : CMMG .22LR Conversion Kit

18 June 2009, 04:39
I think the majority of us have a .22 LR firearm in the collection or have used one in the past. However, mine have taken a back seat to center-fire variants and have seen minimal use lately. With the cost of .223/5.56 ammo absolutely going through the roof, it makes sense to revisit the lower priced rim-fire round.

CMMG has a .22 LR kit that allows the user to simply replace the bolt carrier assembly with the CMMG unit. The drop-in unit is a blow-back design, as opposed to the direct impingement gas system of the standard AR15/M-16. The bolt stop does not activate with the conversion installed. However, the magazine follower does lock the action open on the last round, but the action closes upon removal of the magazine.


I installed the kit in a frankengun that was an interesting lightweight build, using a Cavalry Arms lower, MEGA upper and a lightweight 1/9 twist barrel. An older Trijicon TA01 was used for an optic. The unit dropped in without any issues. I gave it a fairly heavy application of CLP prior to use and in my first outing and when fired with the right ammo, it ran fine.


CMMG indicates that they test fire each unit with Federal High Velocity Hollow Point ammunition. Ammo that I had on hand was limited to Federal American Eagle High Velocity 38 gr Copper Plated Hollow Point, PMC Scoremaster Standard Velocity 40 gr Solid (lead) and Remington Yellow Jacket Hyper Velocity 33 gr Plated Hollow Point. The American Eagle and Scoremaster ran perfectly, but the Yellow Jackets refused to feed. I would assume that this is due to the higher speed of the bolt created by the hyper velocity round.


CMMG 26 round magazines were used. Externally they are the same size as a standard AM15/M-16, which allows the use of existing magazine carriers. The last few rounds took some extra effort to stuff in, but they ran fine at full capacity.

As I have probably mentioned previously, I'm not a benchrest shooter. I did however, shoot this from the bench for zeroing and the initial function check. Accuracy at 25 and 50 yards was similar to that of the .223 rounds fired from the same carbine. The target I used was a 4" outer circle with a 2" dot in the middle. At 50 yards groups ran around 1.5".

I was hoping that the point of impact with the .22 LR would be somewhat similar to that of the .223. However, at 50 yards the POI was different enough to put it off the 8.5"x11" paper. This leads me to believe that the user must either dedicate a removable optic to the kit, or if using iron sights, dedicate a specific upper to the project.

In addition to the lower cost to feed your AR habit, the conversion kit has some additional benefits. Many, if not most, indoor ranges will not permit rifle caliber rounds to be used. However, they will typically allow .22 LR rounds launched from a rifle. This is also a great way to start out shooters who are new to the sport, youngsters and adults alike. They will soon realize they shooting is fun and they might be more inclined to become gun enthusiasts, or at least understand that firearms are not inherently evil.

Cost of the kit is about $200 and the magazines run about $20 each.