[GWS]

Not to me. A little crimp wouldn't do much more than a decent deburring of the case mouth, and then too much crimp could make the cases hang up on that end, and shiny spots would show up at the mouth. Were your shiny spots in the bottom 1/3t nearest base? Try cycling factory Wolf, or blue box Federals....if these do the same thing you have a tight chamber. (those cartridges are best used in Nato chambers). Order a Small-based sizer from RCBS, and that will likely end the problem....or use Dillon dies (which are always small-based). I had the same problem with my new .308 Remington R25 (DPMS). Added a small-base sizer to my .308 die set and the problem went away. Mine would not cycle Wolf or Federal blue box factory ammo either.

Using my calipers I found that the RCBS small-based sizer only squeezes the bases .001 or .002, in addition to that from a regular sizer, at the very most. Most factory is smaller yet.

You could grind your shell holder down a thousandth or two and size the base down enough, but then you are bumping the shoulder that much more. IME the shoulders are usually bumped too much anyway using regular dies adjusted to "cam-over," for an AR10 type chamber. Small-based dies also allow you to adjust the die out a bit and bump less. That actually would work your brass less. My reloads work super using those dies. 168gr Nosler Ballistic Tips over 40.2 gr of IMR 4895, CCI primer.

I'm betting your chamber is commercial .308...should say on the barrel...which is tighter than Nato chambers. (Trying to squeeze more accuracy, perhaps? Pun intended)