TX200. Happy after various attempts

[sherlock1963]

I have been tinkering with various combinations of Pistons, springs, transfer ports and seals. I have finally found the shot-cycle I really like.

The rifle is a MK1 .22 TX. The piston has a polyurethane 0-ring which give a slightly shorter stroke (81mm) The spring is from a MK3/ProSport (225mm, 3.0mm wire) The TP is sleeved to 3.2mm with portable radio aerial 'tube' About 10-12mm preload.

It is unlikely that this combination would work in a .177 but in a .22 I find the firing cycle very soft, just a dull thud, the scope movement is slight and no noticeable hold-sensitivity. First 20 shots at about 10.6 ft/lb.

Possibly more combinations to try but I am reluctant to disturb this set-up.

I have a MK3 .177 TX and a .177 Pro Sport to mess about with now. If I get the time

[KeithS]

Result ... there's some clever dudes in the air gun world ...

[sherlock1963]

It was mostly trying different combinations of parts. The only re-engineering was sleeving the TP. That was simpler than I expected.
After a few/lot more pellets I have found I can watch the pellets fly at 35+ yards which I like.
There is still some hold-sensitivity though.
If I support the front exactly where the stock screws are then 15.9 and 13.4g pellets have identical POI. I didn't expect that.
More testing required