Finally figured out velocity loss

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M

mrjohns

Member
Jul 4, 2016
200
3
Arkansas
My TX200 was losing velocity from 640FPS to 584FPS. I installed a Tesla piston seal and new breech seals. I was still at 584FPS average. I thought the Tesla seal was a little tight, so I checked piston in drill press and put a fine file to the side of the front portion of seal. I then sanded it smooth. The first shot was 630FPS. After 9 more shots , the avg was 616FPS. That is a 32FPS gain. Tomorrow i'm going to do it again and check it with a caliper. Today I just took a little off, to see if it made a difference.
I polished the compression tube and did everything else I could think of, before I stumbled on this fix. I'm getting pretty good at breaking down a TX200. 
 
With those velocities, I presume your TX is a .22. 

It sounds like the new piston seal was so tight it was slowing down the piston travel speed.

re. uniondr's comment, did you check how smooth the bore is? Maybe polishing the inside of the bore would have been a better way to loosen up the fit. But then, it wouldn't be a stock gun any more, and you'd be stuck using the bigger seal sizes forever.

This is always the tricky thing about .22 springers. They're either magnum class (and thus very heavy and harder to shoot) or they're not shooting fast enough and have a loopy trajectory.
 
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It is a .22 and shot pretty good until recently. It might need honing but, I would not know what I was doing, so shaving a little off the piston seal is something I am able to do myself. If I screw-up the seal it wont cost much to replace it. If I screw-up the compression tube it would be around 60 dollars. What is bothering me is the velocity spread is about 24FPS. It use to be about 6FPS. The barrel bore is not a problem. Before the first piston seal went bad, the TX would shoot under 1/2" at fifty yards. I bought the seal from James Macarri, but he can't know if my compression tube is under sized or not. I don't think Air Arms made all their compression tubes on the TX200 , the same size on the inside diameter. 
 
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