Quote Originally Posted by Scrinja View Post
Recently I stripped an earlyish gun (127xxxx serial no, around 1992/3 production) and also a later one (165xxxx, around 2005 production). The stroke of the 30mm diameter piston in the earlier rifle measured around 63mm, while that of the later gun came in at around 84mm. The piston mass for both was a portly 396g, while the inertia weight inside weighs around 73g.
Interesting stuff, Scrinja, I'd only ever known of the 90 using two different stroke lengths but now you've told us of a third --- could the 63mm stroke version be for the German market ?

I'll nip out and measure mine in a bit if it stops raining.