There are many ways to upgrade and mod a 1377. The gun might do 5.5 FPEin stock form, but it isn't out of this world to mod them for about 20 FPE. That's plenty of power for a properly placed head shot on a coon at close range.
Power mods include steel breeches, enlarged transfer port, larger calibers and longer barrels, metal pump pistons, and modified valves. All can be done yourself and fairly cheaply. The grips and cosmetics get a bit more expensive.
In another thread you asked about taking squirrels with it... only do so if you're going to make strictly head shots from 15 yards or less.
VERY fun in the off-season. I suggest you visit this website and learn more. You'll love it.
http://www.network54.com/Forum/275684/
crosman 1377c pellet pistol upgrades?
