What is the fps on a crosman 66 powermaster air rifle?

The FPS listed by the manufacturer is 680 FPS For BB's and 645 FPS for pellets. Field testing produced different results which can be seen below.

1. Gamo Pro Magnums, 7.9gn <--- Pellet Type

5 pumps: High 483, Low 475, Average 479, Difference 8

10 pumps: High 613, Low 586, Average 598, Difference 27

2. Crosman Wad-Cutters, 7.9gn <--- Pellet Type

5 pumps: High 475, Low 465, Average 471, Difference 10

10 pumps: High 601, Low 591, Average 596, Difference 10

So depending on the pellet type and number of pumps the FPS is between 465 on the low side and 613 on the high side with an average of just under 600 FPS for pellets fired after 10 pumps.