I have a DPMS .22LR upper that will not feed properly.  Manually charging feeds just fine, but the bolt does not move forward with enough force to chamber a second round.

I'm using it on my 9mm lower.  Could the difference in 9mm and .223 buffers cause this?

Thanks for you help.

I doubt it.  I'm not familiar with the DPMS bolt system, but I assume it works like the Ciener and the .223/9mm buffer and spring don't move at all (and wouldn't even need to be present).

Sounds like a weak recoil spring in the .22 upper, or possibly a burr or something causing it to drag.  If pulling the bolt back and letting go works it could be that the ammo is too light to push the bolt all the way back.  What ammo are you using?