I have an old M261 22LR kit. Threw it in an upper and ran out to the range today to find out black dog CMMG style mags don't work.

What's the best mag for these? I did find Black Dog has a M261/Olympic mag.

Well they used old 20rd GI mags to put the insert in.

M-261 mag inserts actually work quite well.

That is correct. Those are $50 a pop it seems.


Black dog M261 are $24 a pop.

https://www.sarcoinc.com/m261-magazines-10-round/

The Black Dog Machine magazines get good reviews and I only remember reading of only a couple of issues over the years with the Olympic/261 magazine.   The biggest disadvantage to the original M261 magazine is that it is only ten rounds.   I haven’t used a M261 conversion but I was forced to use the ten round 22 LR Ciener and DPMS 22 LR ten round mags during the AWB.  For bench use the ten round mags are fine but if you don’t live in a ban state I would buy a cople of the BDM M261 mags.   Just don’t let the BDM mags get around certain cleaning fluids like brake cleaner which dissolves the BDM plastic/polymer.   One nice feature of the BDM magazine is the bolt hold open follower.  The BHO follower saves a lot of wear from dropping the hammer on an empty chamber which shortens the life of firing pins and can ruin a barrel or chamber insert on a conversion.


https://www.blackdogmachinellc.net/olympic-m261.aspx

Good info. I love my BDMs for the CMMG. I'll grab a couple M261s from BDM.

Got 2 on the way to try.