I have a RRA 9mm upper on a colt LEO 9mm lower.  I am using the RRA mag block, buffer and spring and modified Uzi mag.

It will stove pipe on every shot!  Bang, stove pipe, clear jam...bang, stove pipe,clear jam..and so on.

It is trying to feed the next round but the stove pipe stops the round from getting fully in the chamber.

I have tried diff. ammo...cheap ammo, expensive ammo, surplus ammo.  Nothing makes a diff.

I even put the stock buffer and spring in thinking that the lighter buffer would maybe help...nope..same thing.

Anyone have any idea what is causing this?

OH...the upper is NEW!

thanks in advance
medcop

I talked with one of the owners of RRA at the recent SHOT show and examined a 9mm conversion unit. One of the items was a piece of Derlin (high impact plastic) about 2 inches long that fit in the buffer tube behind the spring. I questioned what this was and he stated that his tests had show this piece was necessary for reliable functioning. Why, I don't know, but I suggest you give RRA a call to discuss.

Sounds like a mag problem to me. How many did you use? If only one, I'd think real hard about this being the prob.