Two guns

[JPSAXNC]

A Crosman 1400 and a Crosman 140. I had converted both guns to aluminum o-ring sealed pistons, and pin type poppets like the IZH53. The pin .172 od has a much smaller sealing area than the quad seal so the trigger pull is much lighter at high pressure. the 140 shot 772 fps. yesterday on 10 pumps with 14.3 CPHP's, the 1400 shot 660 fps. on 10 pumps with the same pellet. the 140 builds pressure faster, I think because the valve volume is a little smaller, but  doubt the difference in valve volume can be more than 1 CC. 8 pumps on the 1400 gets 630 fps. so the 1400 is only gaining about 15 fps. per stroke for pumps 9+10. I don't understand what the difference is between the two guns?

[JPSAXNC]

The pin valve should have said a copy of the 46M not 53.