760=1377?

[Allan]

but with 7.4 grain, which will up the speed from the standard 7.9

[ustilago]

By filling in the bleed hole, taking the 90* corner out of the exhaust port and lightening the valve spring, I had my 1377 up to 650 fps with Crosman wadcutters through the stock 10" barrel. Of course, that took 50 pumps. The pump cup doesn't appreciate that much pumping.

The Crosman 2100 came with a metal and plastic pump piston. The plastic part is identical to the piston from a 13xx or 2289. The metal portion can be adapted to fit 13xxs and 2289s. (Crosman part # 2200E016 or something like that).