I am rebarrelling an old 6.5x52 Carcano with a .264 barrel and re-chambering to 6.5x54 MS.....my question .....with the case shoulder moved forward the appropriate 24 thou. to correct headspace would the extra 3 thou. expansion at the web ( to bring it up to the same as the MS case )be too much and be an unsafe amount ??

Roger

This may be of some help.
About 1967 FB chambered what should have been a 6mm X 06imp. Well he went .050" too deep. He said all I had to do was use .270 cases and seat his 110 grain bullets out far enough to jam into the rifling.
I did this the first go round but later just sized down the neck to get head space. Either way I was moving a lot of brass forward, and had no case stretch problems.
I also used 6.5x54 Norma reformed and trimmed brass In my Carcanos. No problem roger

I always considered the 2 rounds having the same base dia.
I know the data sheets show a couple .000 difference sometimes, but they often do on metrics and you never know what a Milsurp chamber may hand you.
FWIW, I had a nice orig condition Carcano rifle many years ago that the former owner loving shot and reloaded for.
His brass was Norma 6.5 Mannlicher Shoenauer unprimed brass that he reformed and trimmed then loaded for the Carcano.
The fired, loaded or new unprimed brass didn't look any different from one another at the base/web area as far as expansion or stretching that I recall.
As I say, I always regarded them as one in the same, just one shorter than the other.
Just what little play time I've had with the subject.

I kept the vast quantity of unprimed and uncut 6.5M/S brass for my '03's and sold off the Carcano w/the loaded and otherwise reformed brase and dies. Wish I still had it now!
It was a pretty nice shooter. Standard .264d 160gr RN.