Longslide please look at the bolt for the XGI in flipflop's diagrams. The bolt lugs of the XGI are massive. Assuming that the steel is of good quality it was certainly unlikely that strength of the action was a factor. Durability could an another factor.http://www.rugertalk.com/forum/f48/mini-30-bore-524/
1) The Mini-30 was originally named the "XGI" before the caliber switch.
2) You can load .308 bullets for the Mini-30, if you want. (Don't take my word for that. Do your own research. My memory isn't what it use to be.)