Yes it would be quite expensive to experiment with seals from different sources ! The new one I bought was from the Chambers air gun spares site and was listed as 28.6mm, and is identical in size, colour, price and part number to the Diana 34 seal !

Maybe a Diana 34 seal from a different manufacturer would be worth a go ?

The thing is the cylinder measures 28.0mm maximum and I was wondering if 28.6mm is too big to even wear in ?

I sized it down to approx 28.4mm thinking this would be safe ( the old one that came out was 28.2mm.), but are there any guns with a seal at 28.2 or 28.4 as std ?

Something else I was wondering, both the HW35k I recently worked on and the Remington have similar internal setups and both have springs with top hats and rear spring guide, both have slip washers and new piston seals and are lubed with ‘bumslide’

The Remington has absolutely no twang whatsoever and if you didn’t see it shoot but heard it, you’d think it was a precharged gun or gas ram
The 35 on the other hand still has a slight but noticeable twang ? The only thing I could think of that could be making a difference is that the Remy has an external metal spring guide between the spring and the inside of the piston, could this be creating additional twang dampening ?

Norm.