If it is still under warrenty I would send it back to Crosman. They will unjam it for free under warrenty. Or Open the Slide so that the breech is open and see where it is jammed, if it is anywehre in the breech area it will be an easy fix :D
While I cannot be completely sure, the Crosman Stinger P9 seems to be based on the Walther P99.
The stinger p9 is good with .12 gram airsoft BBs or you can use .25 gram bbs but then it will decrease the range.
It's a repeater. It's not semi-auto.
Best to take it to a authorized repair center
Wal-mart
I'd say the Crosman Stinger P9. I'm an experienced airsoft player and have been playing for about 2 years now. I've had my trust P9 for a long time, and it always functions flawlessly. Plus, the P9 has a high capacity magazine which is nice because it makes it easier to load and it holds more bbs. The more bbs= less time loading. The P311 doesn't look like it has this feature.
See the link below.
Best to take it to a gunsmith.
The breech area on any gun is the area where the pellet / bullet / BB is loaded into the barrel. The bullet stays here until the trigger is pulled.
on the web of course
yes it does hurt it is 275 fps
A Stinger P9 magazine typically holds around 18-20 rounds of ammunition.