If the "new" PGPs bolt is the same as it was on the "old" PGPs, then i suggest replacing the spring between the 2 ball bearings. That will make it not as hard to pump. But make sure you get a strong enough spring that the bolt doesn't fly back when you fire.
Can you tell me what you mean by "large" spring?
Pumping quick and with force is what i had to do with my "old" PGPs too. If the "new" and "old" PGPs have the same bolt, then i suggest buying a different bolt. I have heard good things about copper T's bolt(http://www.cooper-t.com/)