Knibbs got the TX320S MK1/MK2 piston assembly back in stock so I ordered one along with a TX355 spring.
The Mk.1 and Mk.2 TX200 were indeed designed for sub 12 ft. lb., but had a stroke of 84mm, coupled with the stiffer (8.82N/mm) spring now used in export rifles. Air Arms lengthened the piston stroke in the Mk.3 to better suit export markets, and fitted a softer (5.62 N/mm) spring to keep below 12 ft. lb.In order to have just one spring for the UK, the company fit piston weights according to calibre which, in concert with the long piston stroke, makes the recoil a tad sluggish, and the easiest modification here is to replace the piston weight with a synthetic top hat, and increase preload to 25mm to get 11.4 ft. lb. with 8.4gn Air Arms Field pellets.My TX200 (and the TX200s that took all three top places in the last National Recoil HFT Championship) have extended piston rods to give an 85mm stroke, coupled with the UK factory spring and 41mm of preload.
Hi Jim,In the quote above, you mention that MK1/MK2 12fpe TX's using the same spring as the 'export rifle'. Is this the spring that is in my MK3 export TX? I'm a bit confused given our earlier discussion about cooking breech seals with the short stroke and FAC spring. Can you clarify?RE: the pistion from Knibbs....I'll measure the latch rod when it arrives.
I just bought a new TX200 MKIII and am getting ready to disassemble, clean, and drop in a spring kit. I have a Vortek PG4 HO for it and was curious as to whether anyone here has any experience with the TX and these kits. Experiences and opinions would be great.