HI Agen thanks for that. I found the info about the Spitfire very interesting. The barrels that I bought with pistons are hardly worn and within wear limits. I'm really glad that I asked the question because I was going tojust put new rings and. re-use the parts exactly as they were. So live and learn (just in time)
Now this may be of interest. I was discussing this with a Beesa ""expert"" Yeh!! always had Beesa's mate, know all about them. So I said that I was doing a rebuild and at that stage not sure whether I would make it into an A50 or an A65. Anyway he told me "the only difference mate is the piston" If you put an A50 piston in, you got an A50. If you put an A65 piston in you get an A65. I wonder I BSA knew that or whether this lack of knowledge contributed to their demise.
So let us dissect the word Expert
X = an unknown quantity an spert = a drip under pressure. Glad I had chance to share this with you and hope it helps in the future
Mike