Thought someone else might run into this problem so I figured I'd share it and the solution.
My Impact has been back and forth to FX several times now fixing leaks and upgrading it. Recently got it back and pretty quickly I got the 'puff on the cheek' leak again. Thought it was a breech seal so I ordered some, changed it and went to the field on Saturday. Only to have it puffing again. By the time I gave up and put it away it was getting obnoxious.
This morning I called FX and after a few minutes on hold reached the tech who had serviced my gun. I explained the problem and after some diagnosis he concluded that the pellet probe wasn't going deep enough in the barrel for some reason.
Turns out there's a long rod that connects the block with the pellet probe block. This rod is a turnbuckle (lh thread on one end, rh thread on the other.) It had backed off some and the pellet probe wasn't fully seating. The fix is pretty simple once I knew what to do.
Degas the gun of course. Safe the gun. Take off scope and picatinny rail. The cheek pieces come off. Take out the barrel. Then there's a bunch of screws holding the top plate - loosen these and carefully lift off the long plate, leaving the screws in it. Set aside. Lift the block up off the action and slide the probe end out. Remove the turnbuckle from the block, clean and apply loctite. Reinstall turnbuckle and put the probe and block back in the gun. Close the action. Now adjust the turnbuckle until the pellet probe block is just a hair back from the magazine opening. Mine was so far back I could hardly get to the pellet probe screw. Put it back together. Allow the loctite to cure (24hrs.)
I did one test shot and no puff on my cheek and it's a lot quieter. Once that loctite sets up I'll put it over the chrony.
The tech did say that 1000fps would be too fast for the JSB 44.75gr and that I need to turn it down to around 930fps to keep them stabile.
Yeah, happy!
My Impact has been back and forth to FX several times now fixing leaks and upgrading it. Recently got it back and pretty quickly I got the 'puff on the cheek' leak again. Thought it was a breech seal so I ordered some, changed it and went to the field on Saturday. Only to have it puffing again. By the time I gave up and put it away it was getting obnoxious.
This morning I called FX and after a few minutes on hold reached the tech who had serviced my gun. I explained the problem and after some diagnosis he concluded that the pellet probe wasn't going deep enough in the barrel for some reason.
Turns out there's a long rod that connects the block with the pellet probe block. This rod is a turnbuckle (lh thread on one end, rh thread on the other.) It had backed off some and the pellet probe wasn't fully seating. The fix is pretty simple once I knew what to do.
Degas the gun of course. Safe the gun. Take off scope and picatinny rail. The cheek pieces come off. Take out the barrel. Then there's a bunch of screws holding the top plate - loosen these and carefully lift off the long plate, leaving the screws in it. Set aside. Lift the block up off the action and slide the probe end out. Remove the turnbuckle from the block, clean and apply loctite. Reinstall turnbuckle and put the probe and block back in the gun. Close the action. Now adjust the turnbuckle until the pellet probe block is just a hair back from the magazine opening. Mine was so far back I could hardly get to the pellet probe screw. Put it back together. Allow the loctite to cure (24hrs.)
I did one test shot and no puff on my cheek and it's a lot quieter. Once that loctite sets up I'll put it over the chrony.
The tech did say that 1000fps would be too fast for the JSB 44.75gr and that I need to turn it down to around 930fps to keep them stabile.
Yeah, happy!