Thanks guys,
I was a U.S. Marine for 14 years so every weapon I own gets cleaned like it is going to be inspected after every use. One round or one hundred, ball or blank makes no difference.
Up until recently, the rifles I used for reenactments were used for nothing but that purpose and their barrels were pretty much smootbores. The 30.06 blanks I've been using in my Garands were original USGI, '43 dated and are dirty as hell. But they go bang every time.
I'm almost out of those and will be using modern equivalents as well as current issue 7.62 NATO blanks. I'm delinking a bunch that I have on hand to use in my M1919 and M60E3. I've also bought up a few thousand rounds of the plastic Germanicon blanks. My 1919 loves them, but I'm waiting for warmer weather before I can find out if they work in a .308 Garandicon.