Well there's a lot of little things you can do to make your pgp pump stroke smoother. One thing I did which made a big difference that I notice a lot of pgp pump handles have problems with is the inside, they're usually very rough and not that smooth. I have seen some that are smooth stock, but try taking some fine sand paper and smoothing the inside of the pump handle out. Second check the bolt o-rings and see if they're swolen, even if they're just a little swollen they can really make a big difference in the pump stroke. Another thing you can do is file down the lug so that it doesn't drag on the hammer when you pump it back. You can also try working with some softer springs, but chances are you're not going to do much with that because putting a softer main spring will mean your velocity will drop since there's no pressure adjustment on pgps.
Here's a link to how to do the lug mod:
I'm using the stock spring and my pump stroke is wonderful. I did all of the mods mentioned including polished the body and it pumps wonderful even with the stock spring.
Hoped this helped.