It seems unusual that the stock has 2 recoil lugs...I own 2 670's and the only one with 2 lugs is a 7mmRemMag..The other is a 30-06 with a single lug...I just acquired a very nice 770 in 30-06 and it has a single lug...I wonder if somebody swapped stocks on that one?
You peaked my curiosity

. I picked up my Gun Trader's Guide (slightly older edition - 27th) and turned back to the 670's. It doesn't actually mention anything about the lugs, but in the pictures both the standard and magnum versions are shown with 2 of them.
Thanks for the info about the brass GB. I'll likely just buy a decent amount of them now and hope I don't run out. Judging from the cartridge dimensions it also looks like if push came to shove the chamber could be reamed out to .220 Swift, but I'd rather keep it as is unless someday I flat out can't find brass at all for it.
PS This gun was fairly early in the production line for the 670. It's within the first 8,000 of them made. Perhaps early models had 2 lugs and they switched to a single one later in the production? Just a thought. No reasoning behind it other than the fact that this was supposed to be a budget rifle and budge rifles often have cost cutting measures incorporated over their lifespan.