Crsoman says "Up to 460 FPS" for the 1322 pistol (pellet weight not specified).The 14.3 grain pellet is not heavy - pretty much the standard lead pellet weight for .22 caliber air guns.Check for correct head space adjustment of the FTP.Altitude makes a difference for MSP.s and springers, but Ohio is probably mostly not very high.My 1322 with FTP, 18" barrel, and increased valve volume runs are 484 fps for ten pump and 533 for 15 pumps. However I have the disadvantage of being at 5835 foot elevation. I expect those numbers might be 500 fps and 565 at low elevation.I do not think the larger valve volume is an advantage at low pump counts. In retrospect, I would not have done that.
Just wondered if you deburred the tube slots and holes before installing the valve. Sometimes the outer O ring gets nicked as it slides past the sharp edges and causes a loss of compression on each pump resulting in less air in the valve. I don't have a carbine barrel on my 1322 but with Mellon set up and a 12" barrel it gets 495fps on 8 pumps and 525fps on 10 pumps with 14.3g pellets. I have had a number of 1322s over the years that responded differently to mods but your numbers do seem lower than they should be. I got around 600fps on one with a rifle barrel, ice maker tube transfer port & Mountain Air Flat Top set up at 12 pumps a while back. I wonder is the LW barrel choked? Would that make a difference as I only have Crosmans?
Try JSB pellets, as they are much softer and of more consistent quality compared to Crosman pellets.They should zip out faster from your choked barrel.
Hi,my 1322 with 18 inch barrel:10 pump 520fps17 pump 581fps20 pump 602 fps23 pump 614fpswith jsb 14.3greetings Andi
As additional data, at my altitude, with 20 pumps -561 fps, and with 25 pumps - 599 fps.Some air retained with 20 and 25 pumps. More spring!
My experience is the choked LW barrel will reduce the velocity by about 20 FPS.So you're not that far off as you might think.The best method to make power with a short barrel and 10-15 pumps is lower the valve volume.This will increase the pressure in the valve and release it quickly.Experimented with a 13xx gun with various barrels/calibers here:https://www.gatewaytoairguns.org/GTA/index.php?topic=164421.0
The weak link on the 13xx pumpers is the pump arm link.It's about .050" stamped mild steel (beer cans?) and the secondary link can crack or bend if pushed hard.In my experiments I modified a 70s era NOS 766 pump link.It's about .060" with a straight secondary link.I use them on all my modified pumpers.Here's another experiment using a 3/4" tube and 3 1/2" stroke.Uses both a cup seal and o-ring seal piston for comparison.It's equivalent to a 5" stroke 2100.https://www.gatewaytoairguns.org/GTA/index.php?topic=177024.msg156004326#msg156004326A lighter valve spring and an MRod valve stem will release higher pressure.The stock valve stem is soft and will take a set and require more force to open the valve.