Got my stamp so I took the Sig brace off and put on a mil spec Magpul stock, buffer and buffer tube. Now my PWS is a single shot! Tried five different  types of ammo and still a no go. It will eject the spent case most of the time but  will not pick up a round out of  any mag.I have. Any ideas?

Check the buffer spring length. Could be you have the incorrect (or out-of-spec) length spring installed. Happened to me once during a stock install.

Background: I installed a new LMT SOPMOD stock. Buffer spring that came with the stock was not "in-spec". It was about an inch too short. This allowed the weapon to fire, but the buffer spring did not have enough power to overcome the force required to strip the next round from the magazine.

I too had an LMT action spring that wouldnt strip the top round in the mag when loaded to 28 rounds. Sometimes you just get a bad spring.