M4 conversion question

[Rikkrack]

Ok, Thought was a good place to start. Wife has a Bushmaster M4. Is not modified at all. She is reading 299 Days by Glen Tate (great book by the way highly recommend) and read a section where the author converter his Colt AR-15 from .223 to .22 for his daughter to learn how to shoot with the AR-15 platform. She wants to know if anyone knows is this possible and where to get more info for the M4 conversion. First place I go to gun question is INGO, so I know you guys know if it is possible and where I can get more info. I read that you can get Glock conversions to fire .22 with the Lone Wolf. I am new to a lot here so I am not sure what information on the net is good and what is just trying to sell you something.
I didn’t find a thread on the M4 specifically and wasn’t sure if there was a difference on a conversion kit from say a Colt.

Thanks

Rick

 

[henschman]

There are two different ways to do it -- a .22 LR bolt insert, or a .22 LR dedicated upper.

The bolt insert is the cheapest option. It replaces the bolt carrier group of the rifle. You just pull your old one out and stick the .22 conversion in it's place. The forward end of the conversion unit inserts into the chamber of your rifle. You use .22 mags that go with the conversion, and fit the standard AR mag well. The downside to the bolt conversions is that AR's usually use a 1/9 or 1/7 twist rate, which are both much faster than optimal for .22 LR. .22 is better with a 1/16 twist rate. This, along with the fact that the 5.56/.223 bore is actually a bit larger than .22 LR bore, mean that you won't get the same accuracy out of a bolt conversion as you will out of a rifle that is designed to fire .22, like say a Ruger 10/22. In fact, if you have a 1/7 twist, it might not group at all. The 1/9s (which most Bushmasters are in my experience) work OK. You might get 4 MOA or so out of it. I have seen my friend shoot Expert on the Army Qual. Test with a 1/9 DPMS M4gery at an Appleseed. Just don't expect to win any accuracy competitions with it. Another downside is that some of the units are not built very well. My friend's bolt conversion broke twice.

The other option is a .22 LR dedicated upper. That is a whole new upper receiver that pins to your AR lower. This will give you a barreled action that is actually chambered for .22 LR, with a proper .22 twist rate and bore size. They are also usually more durable than a bolt conversion. This is a better option in my opinion, especially if you want to give it a pretty high round count... but it does cost more.

CMMG makes both the bolt conversion and dedicated uppers. Nordic Components is another place to look.