Quote Originally Posted by T 20 View Post
The Airsporter threads are definitely the same pitch but the plug is about 0.22 mm smaller in diameter than the pre War underlever threads.

The Airsporter back block wouldn't screw into the back block of my Webley MK3 cylinder as the threads didn't match --- the Webley threads being finer are probably some weird German thread form.




All the best Mick
That's helpful too, thanks