I have been reloading for my 300 rum, and have always used new brass, until my gunsmith asked me to make him up some dummy rounds to keep in his shop. So he gave me some once fired cases he had, and I adjusted my sizing die to F/L resize, (as opposed to partial F/L that I currently do) after I resized them, I used my stoney point head and shoulders guage and noticed a new casing measures 4.470 at the shoulder, but my resized cases I did for him measured 4.465. Is this a big deal, and what will the shoulders set back further than factory do? Will he have chambering problems? Or since its for a dummy round doesnt it matter? I didnt know if .005 really mattered.

I think you die is going to resize for SAAMI minimum, where the go/no-go gauge is going to be maximum allowable... it's a headspacing gauge

First off, not sure what your smith wanted these for? Second, your not sure if your FL dies are the "rule" or the chamber of the guy you got them from. If your smith wanted them for his own use for bullet seating or something like that, then yea 5/1000's is alot but pretty normal from what I seen with factory chambers and ammo. I guess it would ahve been best to partial them so you didn't knock the shoulder back more than 2/1000".

I guess it would have been best to ask him his use and if its for general purpose then you did the right thing. What we could do is use your guage and a box of my factory ammo to see the average from remington. You can bring your guage by when you do the COL thing.