Quote Originally Posted by Brian Dickicon View Post
The threads are different. I think you'll find some rounded and some flat regardless of whether No.1 or No.4.
Brian, do you have some reference to that? it states in Ian's book TLE Pg 396 that the No4 is rounded & No1 flat & that has been my experience, i do have a No1 with a rounded firing pin but it also has a No4 cocking piece which as a single unit is interchangeable.