I loaded my 375 for years trying every method of sizing to reduce case stretch with full power loads ( I don't see any point in down loading any cartridge) only to no avail.
My concern was not with case life per se, but with integrity with that loaded brass. I was getting upwards of 3 firings but less than 6 firings from each piece of brass because I would discard it after the 4th trimming and there were signs of incipient head separations. The cases would stretch and need trimming after every loading and had me scratching my head as to why it occurred so easily, then after some investigation I found my solution, I rechambered my Win Model 70 Classic Stainless to 375 Weatherby, I have NOT had to trim or discard a single case since, most pieces of brass have not increased in length more than .002"-.003" even after 3-4 cycles through the rifle. I am still on the same batch of fireformed brass I started with and it is still not at the max case length for the Weatherby, which is 2.850", because it actually shrinks the neck when fireformed and takes considerable firings to grow again.
I'm very happy with the outcome and don't have to worry about case head separations in dangerous situations anymore.
Cheers.
