Over the lat 40 years I have collected quite a bit of .308/7.62x51 brass as pick ups at ranges. Some of it was from military ranges, Mil-Surp, and public/club ranges. When I would resize this brass, some of it periodically would not fully chamber in my .308 case checker - this would be thrown into a box/boxes. A few months ago I bought a .308 "Small Base Die" to see if I could recover what had turned into several hundred cases in the boxes. The Small base die worked for some - but not for most of those cases. My speculation was that the brass had been fired in Machine Guns, or Rifle chambers with excess chamber space around the bases.
I have been using the NOE Sizer body and bushings for sizing cast boolits for some years now. https://noebulletmolds.com/site/prod...size-die-body/
It struck me that since the base of the .308/7.62 cases were keeping the brass from going into the Case checker after sizing, that ironing out the base bottom/rim slightly would allow the brass to be recovered for use.
I ordered a .470 Body Bushing from NOE - https://noebulletmolds.com/site/shop...-bushing-b470/ Using this, I sized down all the bases on the brass that I had saved in boxes for a rainy day project. Process was much like using a Lee Push through die, where the base/rim was ironed out to .470". Then I ran them through the sizing die again (just in case).
I found this worked well - allowing me to recover several hundred .308/7.62 cases of commercial & Military headstamps that otherwise would have gone to scrap recycling.