The M14 and M1A yank the cartridge out of the chamber very fast and very early in the firing process (while the cartridge is still expanding from the firing). The headstamp on the cartridge gets 'beat up' much more so than most other semi-autos would do. Also, the brass is stretched (as is normal) and weakened more so than the average rifle/cartridge combo of comparable size and power. The upshot is that you won't typically get as many case reloads from M1A fired brass as compared to the same type brass fired from other .308 rifles.