CMMG .22LR Uppers & Magazines

[Eric P]

I have plenty of S&W MP15-22 magazines, and want to build a .22lr using the CMMG dedicated BCG and barrel. Not the .223 to .22LR conversion bolts.

Do these work fine? I heard there is an adapter you need to make the work better?

Cant "legally" buy the 15+ round mags from CMMG.

Thanks

[Hoser]

I have one of the Boonie Packer adaptors. Works as advertised.

[O2HeN2]

Do these work fine? I heard there is an adapter you need to make the work better?
A dedicated CMMG 22 LR barrel has a "neck" that sicks out which the bolt assembly fits over. The .223 barrel conversion has a adapter that sticks into the chamber.

Of course the 22 LR barrels have a proper twist rate which is quite different from .223.

Mine runs great in semi-auto mode and runs well (you have to pick your ammo carefully) in full auto. Full auto requires an optional anti-bounce weight (plus a few extra parts in the lower :)).

I have a CMMG conversion and its predecessor, an Atchisson as well.

O2

[Eric P]

I put a s&w mag in an ar lower and it doesn't seem too secure

[DFBrews]

I have one and it is a blast
the barrel is at 9” so with the sparrow can it sticks out An inch or so past the end of the hand guard.
Only time I have had issues was with some especially waxy bullets in 0 degree weather.





I have plenty of S&W MP15-22 magazines, and want to build a .22lr using the CMMG dedicated BCG and barrel. Not the .223 to .22LR conversion bolts.

Do these work fine? I heard there is an adapter you need to make the work better?

Cant "legally" buy the 15+ round mags from CMMG.

Thanks

[zimagold]

I have a 4.5" barrel cmmg kit and sparrow II under a 9" rail. 1/2 inch of sparrow sticks out just past the handguard. My mini honeybager setup.

I've actually had the best reliability with M&P 15-22 mags. I use a Redi-Mag (Boonie Packer) adapter which allows for last round hold open. It also reduces the mag well dimensions to hold the mags relatively tight. When I bought mine they said it was max spec to allow for tight fit in mag wells. I did have to fit the adapter to my magwell with a little sanding, less than 5min. Seems to work well in every magwell I have tried after sanding.

It's surprisingly accurate and a lot of quiet fun.

Most ammo runs well, but CCI Tactical seemed to be the best combination of accuracy, reliability, and cost.

[FromMyColdDeadHand]

I have one of the Boonie Packer adaptors. Works as advertised.


I put a s&w mag in an ar lower and it doesn't seem too secure

I have a Boonie Packer adaptor too and the SW M&P15-22 mags fit fine. Do you have an upper on?

One thing that I will say, is that you need to mod a charging handle. A standard one will end up getting brass caught between the CH and the bolt. Filling it is with a bit so it is slightly concave to allow the bolt to move freely is needed. I used some JB weld, I think there is actually a dedicated CH for this purpose, but I had a bunch of spare CHs from upgrading older rifles.

[Great-Kazoo]

I have a Boonie Packer adaptor too and the SW M&P15-22 mags fit fine. Do you have an upper on?

One thing that I will say, is that you need to mod a charging handle. A standard one will end up getting brass caught between the CH and the bolt. Filling it is with a bit so it is slightly concave to allow the bolt to move freely is needed. I used some JB weld, I think there is actually a dedicated CH for this purpose, but I had a bunch of spare CHs from upgrading older rifles.

Yes the 22 CH's are filled in with a very mild relief cut. You could use some of that black silicone, for making gaskets . That stuff adheres to anything.

[SAnd]

I put a s&w mag in an ar lower and it doesn't seem too secure

https://arcatch22.com/products/s-w-15-22-magazine-with-the-catch22-adapter
I run a homemade one of these. Works great. They also make spacers that stick on the mags.

[Circuits]

https://arcatch22.com/products/s-w-15-22-magazine-with-the-catch22-adapter
I run a homemade one of these. Works great. They also make spacers that stick on the mags.

The 15-22 mags fit and work with no modifications - they're just a touch loose, but won't fall out or misfeed or anything.

Before the adapters, stick-on spacers, or clip-on shims existed you could just slap on some duct or electrical tape to make 'em fit a standard magwell more snugly.

[AR3S]

Recently built a dedicated upper using a CMMG .22 9" barrel and bolt. It works great with M&P mags and I would highly recommend the Boonie Packer adapter. I considered the spacers that you had to glue to the mags but didn't want to jack them up. Plus having both the CMMG and the M&P 15-22 on the line at the same time is pretty fun. The other benefit of the Boonie Packer is last round hold open after you drop the mag. Most of the adapters I found didn't offer that

As for reliability, I think I have about 500 rounds of bulk pack through it since building it in September without cleaning. All but maybe 10 rounds has been suppressed and it's run great so far. I will say unsurprisingly that it gets extremely dirty though... Shocking I know...

The upper I built is also a good size and weight for younger shooters. Had my friends 10 year old working up drills and he never complained about the weight or getting tired.