Great thread so thanks again. Quite excited now 'cos we have one of each leather/synthetic both .177 and corresponding TP differences.
Got to have a play. Seem to remember doing it when the leather version was stuck around 4.5 Ft.lb. and needed jaw void sorting.
need to consult scribbles.
THE BOINGER BASH AT QUIGLEY HOLLOW. MAKING GREAT MEMORIES SINCE 15th JUNE, 2013.
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Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
you need to measure your own rifle mate, there's a bit of variation. mine was around 6mm. just see how much clearance you have from rear edge of cocking shoe, to the piston cocking slot rear edge. Whatever that is, you can increase the stroke by (allowing 2mm for clearance) without any further mods. Then measure the height of an hw 80 seal, compared with the leather nose, and then work out how much metal you need to remove from the piston for it to add up.
Piston still has plenty of engagement with the rod... if worried, just buy a new synth HW piston/seal.
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
Thanks! Measuring is probably (like always) a good idea before I start cutting metal! Just curios to know what other people have found and done.
I've already converted to a synthetic seal, and the rifle is a transitional 1980 gun with a small transfer port.
Buying a new piston is not an option right now, since I've already overspent on airgun parts lately
Sorry for the late reply, evert --- my bad.
71mm just happens to be the longest stroke I found that I can take a HW35 out to without any stock or breech modifications.
When changing a leather sealed piston (having a 65mm stroke) into a synthetic sealed piston (normally a 69mm stroke) I have to chuck the piston up in the lathe to machine it anyway, so it makes sense to machine up to a 71mm stroke while I'm at it.
The HW35 has the same length cylinder as the Old School HW50 which uses the same cocking arm as the 35 and also has a 71mm stroke so there's no issues with the cocking arm at the longer stroke.
All the best Mick
No problem!
I have done the conversion, and machined down the front. The pin that goes through the piston body/front/stem was the determining point for me, didnt want to weaken the surrounding material too much, and left a conservative amount of piston ahead of the pin. Ended up with a 69mm stroke, and had to remove som material at the rear of the piston slot for cocking arm clearance.