This is the gun that I left cocked for an unknown time. IIRC it was shooting 7.33s at around 710 fps a few weeks ago. After I found it cocked the power was down 30 or 40 fps. Yesterday I chronographed the gun at 666 Avg before setting off to replace spring. I took the gun apart and put a fresh spring in it and it only averaged 685. Not a colossal gain and not anywhere it should shoot with a new spring.
The gun felt jumpier than it should at that velocity. Like it didn't have enough back pressure. I knew something was wrong. This time I took it completely apart and removed the piston. That showed a long score along the bottom compression tube in seal travel. A metal chip got stuck in the seal and carried up and down the tube. There was my pressure bypass.
I cleaned the metal out of the seal, filled the score, honed the tube and reassembled the gun with the old spring and seal. After ten or twenty shots I chronographed it again. A ten shot string went AVG 716, ES 8 and SD 2. Right where it should be. More importantly the gun has a nice smooth cycle again.
Apparently leaving the gun cocked perhaps for weeks didn't hurt the spring at all. It must have developed that score after I chronographed the gun weeks ago. I have no idea where the metal chip came from. This gun is 8 years old and probably has 100k shots on it. Maybe it's from the spring that's not very old.
Live and learn
Be well all
Ron
The gun felt jumpier than it should at that velocity. Like it didn't have enough back pressure. I knew something was wrong. This time I took it completely apart and removed the piston. That showed a long score along the bottom compression tube in seal travel. A metal chip got stuck in the seal and carried up and down the tube. There was my pressure bypass.
I cleaned the metal out of the seal, filled the score, honed the tube and reassembled the gun with the old spring and seal. After ten or twenty shots I chronographed it again. A ten shot string went AVG 716, ES 8 and SD 2. Right where it should be. More importantly the gun has a nice smooth cycle again.
Apparently leaving the gun cocked perhaps for weeks didn't hurt the spring at all. It must have developed that score after I chronographed the gun weeks ago. I have no idea where the metal chip came from. This gun is 8 years old and probably has 100k shots on it. Maybe it's from the spring that's not very old.
Live and learn
Be well all
Ron
