Chinese airgun forum: "1377
4 pumps = 410 fps
6 = 485
8 = 525
10 = 560
12 = 582

HB 17
6 pumps = 400 fps
8 = 438
10 = 470

B5-10
4 pumps = 578 fps
6 = 660
7 = 682
8 = 706

I didn't go beyond 8 pumps on the B5-10 due to 'neighborhood constraints' on a Sunday afternoon as it was getting late (and loud)."