I finally finished up my rear spring guide and tried it out, the spring was coil bound just before the sear engaged. It took another trip to the lathe for some fine tuning but I'm calling it finished.
I assembled the parts for a test fire and after about 10 shots everything is looking good. I am going to tear it down again to check things out after I shoot a string over the Chrony. I want to make sure everything is working like it should.
A 10 shot group over the chrony and I have a base line. 10 RWS Meisterkugeln 8.2 grain pellets gave me an average of 667 fps, and a good group, 7 of the 10 pellets went into a nice small group. The FPS seems a bit low, I was expecting closer to 900 fps.
It appears that the O ring seal isn't working as well as I hoped, I'm going to try a few changes before I give up on it.
Once I get it torn apart again I'll get more pictures and give more details so stay tuned.....
Rick, I also have this very same.. or very similar Air Rifle. I have found a guy in Australia that will make a custom piston seal for about $30 + postage. he is sending one up to me in the next few days to try out.
ReplyDeleteHe is on Ebay and goes by the username Customairseals. I hope this helps. He is sending me a 30mm HW seal and adapter to fit the Gamo Magnum. He said I will need to "Tune" the seal by reducing its diameter to match the compression chamber. He said to use a drill and some fine sandpaper to evenly reduce the diameter.
ReplyDeleteNice! Let me know how it works out. This project is on the back burner for now but I haven't given up on it.
DeleteWill do,
ReplyDeleteCheers Mark
Can I ask how you got the screw out that holds the piston seal in place. My seal was in similar condition to yours. The screw seems to be very very tight. I don't want to risk damaging it. Might try some heat.
ReplyDeleteI don't remember it being difficult to remove, I have had to use heat to help remove Loctited screws. For those who aren't familiar with Loctite, I use a small butane torch to heat up the head of the screw. No need to get it red hot, just get it hot. I let the heat soak in for a few seconds to soften up the Loctite then try to remove the screw. Repeat as necessary.
DeleteHey Rick, sorry it took so long to get back to you. Well I did get those seals from the guy in Melbourne. He could not do a 29mm seal, but sent me a 30mm seal that I had to shave down myself. He send me two practice seals as well to get my technique right. I tried one of the practice ones and fitted it up. It worked pretty well for a while then the performance dropped off considerably. I think this may have more to do with the poor spring quality. The spring is very bent and misshapen. Might try looking for a new spring .. I did manage to find a supplier for a genuine new seal and have ordered it. It is coming from the UK. hope customs in Australia don't hold it up. See how we go with that. BTW, I got that screw out. Had to drill it out...the head was the part that was stuck in the main tube. Even after drilling a hole through the center and getting the two halves apart, I had to belt that head out with a hammer and punch. Found a new screw in the local gun shop air rifle parts bin. Cheers Mark
ReplyDeleteIt seems like some airguns are a lot of work just to get shooting and fight you all the way. Mine is still waiting for me to tear into it again.
Delete