AR Build 9mm and .22LR

[johhny12gauge]

So my friend wants to build an AR in 9mm and .22LR. I have had 2 Bushmaster Carbon 15 9mm's and a 14.5" .223 Eagle Arms. Unfortunately I know nothing about how ARs work. So I was thinking he should buy a complete lower off the exchange for $3-400 as a starting point. Than maybe buy a Chiappa upper for $375. This should work fine right? so .22LR conversion is done.
Now if he wants to shoot 9mm where is the best place to get a cheap complete upper? Does he need more than just the Upper/mags to make it work? Thanks

 

[Claven2]

He is better off with two complete guns as it's a PITA to change out the hammer every time you do an upper swap IMHO.

 

[ridgearms]

I believe you can get a ramped bolt for the 9mm so you don't have to swap hammers no?

 

[Claven2]

A ramped bolt is a compromise that will only delay and not prevent the hammer-pin hole from rounding out.

Use a 9mm hammer. They were invented for a reason.

 

[667]

a "no notch" or standard 9mm hammer should work well for both a 9mm and a .22 upper... At least they do with the .22's I've used (Tac-Sol)
For the 9mm you'll have to get a mag well adapeter as well as a different buffer/spring