Diana 440TH, 28mm piston, 76mm stroke, 4mm TP 5mm long, piston weight 215g all in inc seal, shot cycle is like a schung!!! when you fire it, barely moves, follow thru on 35yard targets .177 is easy, you can watch pellets drop off targets.
Diana 440TH, 25mm piston, 80mm stroke, 255g piston, TP as before, near as good BUT different, more dull thud like a 97, i like it but not as much as the one above...will make an alloy piston for this one.
Diana 52, .22, 75mm stroke, 25mm piston, 265g, 4mm dia 5mm long TP, shot cycle fast, smooth, very slight recoil, best .22's i have...
All these guns are better than my 97's, and way better than the TX I had (which was nice but you guys have pushed that forward now) and the reason?
The ultra short transfer port
and the fact Diana comp tubes are machined from a billet so never leak (apart from the port seal)