usp compact

I have a new KSC usp compact tiw build, I have gathered from what I could find that the gun does not like propane in stock form.

When I gas the gun up with propane, the first 5 shots come out good, after that slide still cycles, but bbs roll out of the barrel, once in a while shoot out ejection port.

Is this because of the propane? I plan on buying metal slide kit, and upgraded hammer and recoil spring. Will this solve my problem, I also was thinking of installing high flow valve in mag before I get the slide and spring upgrades, will this help or just break something?

Any body have any insight on this problem?

[hattrick]

From my exp w/ the compact, dont go for the high-flow\

Dont single fire the hammer while its decocked, or not cocked at all. (i hope you know what i mean)
It'll result in a broken trigger

Upgraded piston return springs might help a little.

[swatt13]

sounds like the air nozzle or hop up are messed up, manually cycle the slide and ensure they are engaging properly with out a mag and then with.