Has anyone sucessfully converted their 15-22 upper to work on a real AR-15 multi cal lower?

It is a close fit and appears to work but a little mod will need to take place to make it fit correctly. Basically it look as if the front pivit point on the 15-22 upper needs to be reloacted correctly or enlarged (incorrectly IMO) to make it work. Mag feeds rounds fine and all else seems to work in my quick testing.

Looking to SBR a lower and well you get the multi cal picture.

If your saying that all that needs to take place is enlarging the mp front pivot hole, that should be and easy mod. Now who wants to try this????

can you post pics of the two lowers guts side by side and the ar lower under the mp upper?

Evening reel adventure

I haven't tried to put the 15-22 upper on any of my AR lowers but assuming it will fit as you suggested I have serious doubts the bolt hold open will work.

While I haven't any experience putting the 15-22 upper on the AR lowers I have a fair amount of experience putting CMMG 22 uppers on the AR lowers.

I occasionally use the 15-22 mags with the CMMG lowers so the mag is placed in the AR lower in the same place you will end up as the AR lower mag well dictates mag position. The mag position in the AR lower won't allow the tine on the 15-22 mag to contact the bolt hold open.

You will also more than likely have to shim the 15-22 mag (a 2mm piece of mylar or plastic) on the upper front of the mag so it stays in proper position in the mag well during semi-auto firing (no biggie as I do it all the time to use 15-22 mags in the AR lower.

If you get far enough to get it working give me a PM as I know a guy that sells custom sticky backed shims to get the mag to fit properly. I also know of a guy that machines custom made bolt hold open latches that with a little fiddling will work with the 15-22 mag to get your bolt hold open to work (unfortunately it then wont allow the AR 223 upper to work without changing back to the stock bolt hold open).

You might look into the complete CMMG upper as the fit on the AR lower is perfect, the operation is great (after getting the mags to work correctly), & the accuracy is much better than that plastic 15-22 upper with the flexible barrel to plastic retainment. It's quite a bit cheaper than the complete 15-22 also.

Just sbr the 15-22

Even if you get it all to fit, there are a couple differences between the 15-22 lower and a standard AR15 lower that will decrease reliability in the best case scenario. 1. The bolt catch is more forward on the 15-22. Your bolt catch/release will probably not function properly because of this. 2. The buffer tube on a 15-22 is blocked off and solid, providing the necessary stop that the bolt assembly needs so that the bolt can move forward and cycle the next round. However, in an AR15, the buffer tube is hollow and has a spring and buffer that move back with the bolt carrier group and then pushes it forward again to cycle rounds. This means your whole bolt group of the 15-22 will move back when cycling. This will cause a lot of jams to say the least.

Thanks for the info. The more I kick it around the more I just want to stay with the mp 15-22 platform. Im sure I will SBR my .223 and prob the scar 17 after this project.

Now I need to figure out do i sell my 15-22 pistol and buy another 15-22 rifle and sbr it or put a butt stock on my pistol. There is a guy on you tube who made a adaptor that said its available on ebay but its no longer listed.

Any Ideas?

Morning reel adventure


A couple of thoughts:

First, check the laws in your state to see if putting a stock on your pistol is legal. (in a lot of places it isn't legal)

Next, try E-Mailing CMMG ([email protected]) as I think they have a short barreled upper that will fit right on your AR lower.

Im good to go here in NC. Already a stamp collector.

Isn't a stock on a pistol a federal issue? SBR?

I dont worry with that federal stuff, they dont scare me.

I buy their stamps instead and I dont get in a hurry. It all goes through my biz inc.

I just wear my tinfoil hat when I play with my class III.

If I remember the convoluted Fed regs correctly you can convert a rifle to a pistol or a pistol to a rifle but on one of them you have to have possesion of the parts that can convert it back, I just don't remember which way is perfectly legal and does not require any stamps. I think the rifle to pistol is the one that does not need stamps as long as you keep the parts to convert it back. There was a case on this not too long ago.

Pistol can be made into a rifle but can not go back. Once a rifle always a rifle. That's why most Sbr Ar's start out as pistols, that way you can still use them and check function and what not.