2289g piston stroke?

[bigfish123]

I have modified 2289g. The mods so far are steel breach poly tube transfer port, 14.5" barrel polished lead and crown. Flat top piston and valve lighter valve spring  extended bolt probe, metal barrel band. I just added the barrel band, now when the pump arm is fully extended I can just see the o ring of the piston. Will that allow enough air intake or do I need to take some metal off the bottom of the "u" or take some off the barrel to allow more extension of the pump arm?

[rsterne]

As long as the piston O-ring clears the back of the slot it will work fine.... If it barely clears you may have to delay a second at the end of the out stroke to let air get into the pump.... You can probably take a bit off the bottom of the barrel band to clear the pump arm.... Removing metal at the end of the slot will shorten the effective stroke and you will pump a fraction less air with each pump....

Bob

[bigfish123]

Thanks Bob that is what I thought also. I haven't had time to shoot over the chrony yet. Before the extended bolt and barrel band it was shooting 14.3 CPHP at 530 fps @ 10 pumps and 580 fps @ 15 pumps. Does that sound about right for these mods? Accuracy  not consistent but has improved with the barrel band. I'm hoping that I can get CPHP 14.3 to shoot under 3/4" at 25 yards  using a 3-9x40 leapers scope.