Is this a good drop in kit?

I have a spare upper and boatloads of .22. Thinking of putting this kit in and just swapping uppers as needed.

Anything to be concerned about or other options to consider?

They're great. Accuracy will be okay for plinking but it won't be match grade out of a 1:7 barrel with a chamber adapter.

They work fine. I eventually bought a dedicated .22 barrel, and converted the kit to a dedicated .22. Accuracy out of a 1/7 twist barrel is crappy, but it is cheap practice.

Bare uppers are still available at normal pricing, and 22lr barrels and barrel collars are available.  Get the bolt group, a barrel collar, a barrel, an upper and some cheap handguards and just build a dedicated upper.

The mag loading is what I despise with the CMMG magazines.

Yep, that’s the route I took. Can ring 5” steel at 100 yards all day.

as commented, the 5.56 barrels will give pretty dismal accuracy... the dedicated barrels with collars much better... I have two conversions...older Parkerized and a stainless... I've used both SW15-22 mags with ReddiMag adapter, but a lot of rounds caused malfunction forming grooves in the feed lip... I currently use the BlackDog mags with the investment cast feed lips and beam welded mag bodies

22 rimfire uses a bore diameter of .220” and a 1 in 16” twist.  223 uses a .223-.224” inch bore diameter and 1 in 7” to 1 in 12”.  The undersize bullet for bore diameter will hurt accuracy and cause substantial leading in your 223 barrel.  The twist too kills accuracy.  I think these kits were meant to train recruits who had never fired or even seen a gun.  They could familiarize them with gun safety and functionality without the recoil and noise of the centerfire cartridge.

If you need accuracy, build a dedicated rimfire upper.

Success is variable.

My little XM177 clone (1 turn in 9") will put 10 shots of Rem. Golden Bullets in a dime sized group at 25 meters shooting prone.

My son's HBAR clone (1 turn 9") will lead up like a mother with Federal auto match.  Took multiple cleaning sessions the last time (and it will be the last time) he shot .22 ammo in it.  Brushing/patches didn't get it done.  Had to buy some lead removing cloths from Brownells to cut into patches and went through almost the whole package before getting the lead out of that barrel).

None of the others I've shot .22 in will shoot like that little XM177 clone.

Like any .22, guy a box (50 rounds) of several different kinds of ammo from different makers and try it out to see what is reliable and gives you good groups.

Two things have help mine.  One is to get the oil off it, grab some lapping compound and put on the rails and work the bolt back and forth on the rails a couple hundred times (add more lapping compound as needed) to polish those rails and then clean it all off and add lube before shooting.  The other is, in at least one AR we found the bolt was rubbing the right feed lip on the Black Dog magazines resulting in failures to fully chamber.  Used a pocket knife (at the range) to scrape some plastic off the top of the right feed lip till we got enough clearance to allow the bolt to move freely.

I use the CMMG bolt in a dedicated .22 I built. The bolt works fine.

BTW, I love that gun. It's one of my favorite ARs. I strongly encourage you to go with a slow-twist barrel, though.

Thanks for all the input!

Seems like that while the drop in kit works, there are some drawbacks. (Accuracy and lead fouling of the barrel most notably)

I've put together a few uppers for .223/5.56, never assembled a .22 upper, but would like to give it a go and have a dedicated upper.

Any tips or tricks to assembling one of these? Recommendations on  the parts/barrel  or suppliers?

It took me a while, but I finally got those grooves in the feed lips.  Part of the reason is that the S&W magazine spring is a much heavier weight than the BDM item, so the rounds' rims get slammed into that polymer with much more force than that generated by the BDM spring.   I still use S&W magazines, but I consider them wear items and buy when I see them on sale.

I've found no other magazine that will work the bolt catch reliably.

CMMG is who I used for my barrel. A company called velocity firearms has .22 barrels in stock.
This might be helpful in answering your questions about .22 uppers.

I dropped the conversion kit in my 7.5" and it worked just fine. Within 6 months, I bought the collar and a 4.5 " barrel for a dedicated upper. The S&W mags work without the adapter in my early run Aero lower. It was too tight to fit the adaptor. I've been shooting it like that for a couple years. The S&W mags are sooo much faster to load and easier.

Dude.  I have thoroughly tested this device.

Mag loader

There must be some rock city where all the inhabitants live under a rock.

The CMMG drop in kit that is STAINLESS STEEL is awesome!

You can buy a trip lever, counter weight, and appropriate springs to run them with a binary trigger.

This loader rocks!

Try this for a mag loader: http://blackdogmachinellc.net/lightnin-grip-loader.aspx

Also cmmg stainless steel kit for $169: https://www.joeboboutfitters.com/CMMG-Bravo-SS-Conversion-Kit-w-25-round-magazine-p/cmmg-22ba6e1.htm

You don't need a gas system.  Only need a gas block for a place to mount a front sight or to hold a end cap in place to hold hand guards.

righttobear.com usually has all the goodies or at least when they are in stock they do, both their brand (rebranded cmmg) and cmmg stuff.

I got my barrel for my Blaster (tip of the hat to the Star Wars look) from these guys, shipped next day and works just fine.  Comes *with* the barrel collar which is cmmg compatible, so that is a $40-50 savings  - https://www.velocityfirearms.com/product/ar22-m4-barrel/

Have one of those loaders. Thanks.

Same.  Had one for about 10 years

Zero malfunctions.

Tried to shoot one of those revolutionary war shoots with one and it wasn’t accurate enough to do it.

I love my drop in conversions.  I have dedicated uppers as well but find the accuracy totally acceptable for running drills with my favorite ARs in .22.  Get the lightning grip loader and the Cmmg/blackdogmags load beautifully.  I’ve never converted anything to the S&W mags because I’ve never had a problem loading them and they all function 100%.

I had a better mag adapter once for the SW mags. Love the mags, do not like the adapter so I sold it. I just shim the SW mags and use them without the better mag. I am thinking of getting one of the new style catch 22 hold opens. They give you hold back without all the intrusion that the better mag adapter creates. The Catch 22 only holds open on the last round with the SW mags and maybe some from Kriss maybe?  

Last round hold open is not all that important to me anyway. I have Black Dog straight and Black Dog drums. I run them with no problems. Drum has a reloading assist and is easy to reload. Black Dog straight mags are really not all that hard to load either..

First time out I ran a dropin conversion. Soon I bought a barrel, and collar and went dedicated. I never had any real problems with the drop in. Accuracy was good enough for a plinker. Just wanted the dedicated upper instead.

I still use a dropin occasionally with my binary setup. Just to save wear on my dedicated uppers, as you are not really shooting much for accuracy with those anyway,LOL

If you are only going to have one AR22. I would just go dedicated from the start however.

I also had a problem fitting the BMA in an Aero lower.  I just had to radius the front two edges of the BMA and it slides right in.  Did not affect it for use in other lowers.

I built one a while back with a CMMG kit.
Worked fine to the day I sold it.

My drop in kit works perfectly on a m16a1 upper (1/12).. same poa/poi.
It sucks on the 1/7 upper.

Copper plated bullets help a bit with lead fouling.

I don't have a CMMG conversion kit but I do have two of their dedicated barrels and bolt groups...one in a 4-1/2" plinker pistol and the other a 20" service rifle upper that I use in rimfire sporter matches.  Both are reliable, fun and the 20" will hold the X-ring on a B-19 target (about an inch in diameter) at 50 yards.  I run the Bore Buddy stainless weight and recoil buffer in my 20", along with a Better Mag Adaptor (BMA) and MP15-22 magazines.  On the 4-1/2" plinker I also run the BMA but there is not enough port pressure to cycle the bolt with any additional weight installed.  I shoot CCI standard velocity in the 20" exclusively but if my supply runs out, I'll probably switch to one of the Eley offerings.  In the plinker, I run all my other 'junk' 22 ammo and it eats them all without complaint.  Some careful polishing of the barrel collar feed ramp as well as the bolt rails will enhance reliability.  I use a Dremel with some jewelers rouge but be careful on sharp edges of the feed ramp...you can round them off easily.  I got a little too aggressive on one side of the top of the feed ramp and it's a bit lower than the other.  Hasn't affected reliability but I wish I'd been more careful.

I typically clean the 20" after each match - about 60 to 70 rounds - so I don't see much in the way of leading (at least that I can see) in the barrel.  Most of my effort is spent on the bolt, ensuring that it's clean before the next match.  Some folks seem to think that cleaning the bore is a waste of time and may affect accuracy...not sure if it really matters at my skill level.  I have not yet cleaned the plinker as I only finished the build a couple of months ago as the ammo shortage was beginning to take hold.  Thus far it has eaten about 400 rounds and I'm saving what is left of my ever-dwindling ammo supply.  It will get only an occasional outing until the supply situation improves.  It's kind of a lousy time to have a pistol that eats ammo like crazy.

I think CMMG has done a fine job in their .22 offerings and you won't be disappointed in them.

Informative thread.  Thanks everyone for the info.  

It sounds from a post above that the Right to Bear barrels are just rebranded CMMG. Is that confirmed?  Any expected performance difference or are they literally the same aside from brand and profile (I see RTB offers a 16 light weight).

FPNI. Good to go. Lots of fun for plinking, training, teaching new shooters, etc.

ETA: Never had any issues loading the CMMG/RTB magazines but..? It’s the same pain that loading any .22 magazine can be. Can’t confirm that the RTB parts are rebranded CMMG but they look.. suspiciously similar?

Doesn’t shooting 5.56/223 after shooting .22lr blow out all the lead build up?

Um, no.  But it can spread it nicely along the whole length of the barrel.  Best way to avoid lead buildup with 22 LR is to shoot plated bullets, or shoot a barrel properly sized and rifled for 22 LR.

Not exactly.  According to SAAMI the 22 LR uses a .217" bore diameter and a .222" groove diameter where the 223 uses a .219" bore diameter and .224" groove diameter.  The 22 LR bullet diameters can vary from .2215" to .2255", although most are right at .223", so there can be some gas blow by which may result in some lead residue with naked bullets.

All of these.

I tried the stainless CMMG drop in kit with chamber adapter out of a 1:7 twist 10.5" AR barrel. Probably 10 different types of .22 and at 15-25 yards the groups were pretty wide open.

A couple years ago I ended up removing the chamber adapter on the drop in kit and bought a dedicated 1:16 twist 22LR nitride barrel from Grid Defense (Someone from the inside of Grid confirmed they were CMMG OEMs). They were running a BF promotion at the time:

7.5" .22LR 1:16 Twist Barrel 7522LR1$59.00 USD
Grand Total:$55.14 USD

I went shorter on the barrel from 10.5 down to 7.5 and still significantly tightened up my groups down to 1-2". I'm a little more confident I can use the dedicated upper for suppressed medium range pest control. If you already have a drop in kit and want to go dedicated its pretty easy to remove the chamber adapter and then the exposed collar mates up with the dedicated barrel upon installation. There are some videos out there.

If you look at the difference in bore size and see how far the rimfire bullet has to jump to hit rifleing the drop in shouldn't work at all but they do work pretty well.

I have had good results but some guys I know had some work to get things broken in.


I find it works better in most cases to not use oil on the drop in as that just catches dirt and gumms up everything. I hose everything down with spray silicone and they run pretty good.

With some brands of charging handles there is binding , just swap out for any old cheap GI style charging handle.

Accuracy will vary , generally 9 twist will work better than 7 twist . Like any rimfire if your goal is accuracy you need to test fire in your gun to see what brand/type makes it happy. Once your unit is worn in a bit it will likely run ok with standard velocity ammo and that generally is quite a bit more accurate than high velocity ammo.


My 1/9 barrels work decent , I bought a old 1/12 thinking it should be better but for whatever reason it shoots about the same as the 1/9. My most accurate upper is a Rock river national match which is 1/8 . This is considered a entry level match barrel so I guess quality wins out?

The dedicated uppers have more accuracy potential but the beauty of the drop in for me is that it will work in all my different style ARs. I have shot my stuff against dedicated uppers, beat some ,been beat by some but the difference isn't huge in most cases.
The blowback action blows lots of crud into trigger and magazine , hose them down with brake cleaner on the trigger and silicone on the magazine and drop in unit.


Short list--- Slower twist, good ammo, lots of silicone on unit and magazines . Have fun!

“They work fine. I eventually bought a dedicated .22 barrel, and converted the kit to a dedicated .22. Accuracy out of a 1/7 twist barrel is crappy, but it is cheap practice”

I shoot a 1/7 twist in a 14 1/2” barrel using a CMMG chamber conversion and Aguila 60 gr. SSS and get great results even with still having the 1 1/4” free bore. You definitely want to get a non gassing charging handle with this ammo if your eye is close to the back of the receiver.

My main "go-to" gun is a 10.5" 1:7 with a can. I'd like to start shooting .22s so I can keep up with training on it. I was going to build a matching .22 dedicated upper, but would like to train with my NV as well, and don't want to purchase another IR laser illuminator/passive optic just for the .22.

Just how bad can I expect the accuracy to be out of that gun, and will it be safe to still use my suppressor?

As it turns out, my main "go-to" M16 configuration is a 10.5" heavy bbl, 1:7, 5,56 upper with a screwed on (discontinued years ago) GemTech TREK-T suppressor.  I've shot some, but not vast quantities, of .22LR through it via a .22LR conversion assembly.  I always run a handful of 5.56 through the upper after shooting max of 100 or so .22LR rounds.  As for accuracy, it's good enough for hitting balloons inflated to about 5" dia. at 25 yards off-hand most of the time.  With that gun, I'm a recreational shooter; for more serious .22LR shooting, i.e., hunting, I use a bolt action rifle.
Best of luck whatever you pursue.
MHO, YMMV, etc.  Be powerful; be well.

Thanks for the info! That's exactly what I was looking for. The way some people make it sound, I was expecting to hear 12" groups at 15 yds.

I've got a dedicated 4" and a savage FVSR if i need to be accurate. Sounds like the drop in will be perfect for what I'm wanting to do with it.

Why? Hard to insert or hold?