It’s seriously called a Kate Moss stock?

Yup, the original Sig skeleton stock got nicknamed the Kate Moss, and it stuck for clones. IMO the $8 or so for the rubber mlok covers on top of the stock is pretty nice. That or 550 wrap it.

Sig and PMM clone

While a throw in conversion kit is enough for me to hit up to 100 yards, I started experimenting with some Aguila SSS ammo (Sub Sonic Sniper 60gr subsonic).  The 60gr rimfire stabilizes well in my 1:9 barrel and quite accurate, beyond 100 yards accurate.  Still the wrong bore size but still almost as good as my dedicated rimfire upper.

I highly recommend a premium firing pin because you will break yours, just a matter of time.  All my kits run well dropped in as is unless I go full auto and then there is some more parts and tweaking going on.

My dedicated rimfire has the CMMG rimfire metal ambi charging handle which is short and has a neck that is almost all solid to block gas, cut port ejection door, moved brass deflector, forward assist accessory on the bolt (which will probably only get me in trouble one day as rimfire gets dirty fast, especially when suppressed and I am tempted to use the forward assist instead of cleaning) and rimfire magazine catch. Some people put a special plug into the FA so it looks normal yet non-functional.  You can get the gas blocking insert for the standard charging handle from Borebuddy, including the firing pins and a lot of other nice upgrade parts.  I don't bother with special parts on my throw in conversion kits except to upgrade the firing pin when the OEM breaks.

If you are going full auto or trying to use it with an FRT trigger, Borebuddy has an adjustable auto sear trip now so you don't have to bend yours to time your carrier correctly, as well as an adjustable anti-bounce weight with removable weights that can be configured in multiple weights.  You need both the auto sear trip and anti bounce weight to go full auto or FRT.  As you can see in my posted videos above, they work well in full auto when properly configured (and the ones in my video have no special parts or tweaking, they happened to work for me quite well)

Btw if you go with a regular lower, the bore buddy ‘plug’ should work pretty well on reducing malfunctions. I used a 2mm silicon bumper on my folder to fill the gap behind the .22 bolt group and it’s been 100% since.

OP wants to shoot to 100 yards.
M&P15-22 and CMMG conversions have really crappy accuracy.

My vote is a CMMG dedicated rimfire bolt (not a conversion adapter) and a Beyers rimfire barrel.
I run mine with a M&P15-22 magazine adapter. Runs great and very accurate.

ETA: used my phone set to high-speed camera mode and a BoreBuddy kit to tune out all bolt bounce.

What accessories/replacements should I buy for my dedicated CMMG .22LR upper?

It came with a solid charging handle. So I don’t think I need a dedicated CH or CH insert. I’m just using a standard AR lower with MBT in it.

The Bore Buddy kit, an extractor kit, and ammo probably.

Likely nothing, but there is bling you can add, subsititute.  I have 2 dedicated uppers and haven't changed anything from what the bolt assembly came with.

With a standard AR lower, you will likely need the BoreBuddy 22lr AR Buffer Pressure Plug:
These parts provide pressure against the back of the 22lr bolt carrier group and increase reliability of both conversions and dedicated 22lr uppers.

Our novel quick insert design allows for one handed insertion and removal without the need for tools.  Simply line up the insertion slot with the buffer retention pin, slide the plug into place and rotate 1/4 turn until the pin sits in the slot of on the front face of the plug.  Removal is is done in a similar manner, pressing in the buffer plug slightly and rotating the plug until the pin lines up with the insertion slot.  The part can be inserted either direction, but we recommend inserting the side with the hollow cavity towards the buffer and the solid face towards the bolt carrier group.


Attached File

How many rounds to CO2 cartridges does that set up burn through?

I tried the Bore Buddy plug, didn't make any difference for me, I didn't need it but it does increase reliability for some.  They also make one for a LAW folder.

Same. I think it's more suited for running the conversion bolt on a .223/5.56 barrel.

I built a dedicated .22LR with a RTB upper and CMMG 9.2" barrel and BCG. I was having what I think was bolt bounce (bolt chambering a round but extractor not staying on rim). I installed the plug along with a Bore Buddy higher power extractor spring and it runs 100% now. Not sure if the plug helped or if it was mainly the spring.

For a 22-- dedicated upper is the way to go. Easy peasy to put one together and accuracy is quite good. You won't  be sorry. CMMG barrel and CMMG bcg throw in some BDM magazines and prepare for some serious fun! Good luck!

I got my upper and barrel from.right to bear arms as well my 25rd mags

Threw it on a lower with a Franklin binary trigger


Fun fun fun