Bart, I agree that for the next GM barrel I use I'll cut the muzzle back slightly and recrown it. The muzzle and the non-buggered screw heads are the biggest tells in my opinion. I finished a Lehigh barn gun lately, even though photos are up on my site, I'm still playing with the aging. I'll share more of that one in a few weeks.
-Eric
Eric, here are some pictures of a barrel I aged along with some other details
It helps to have some old original barrels on hand to get a feel for old barrels. The screw heads on the rifle are the same, but I turned one down, toolk any sharp edges off the head, crunched the side with a pair of pliers, hammerd on them with a hammer. Both started as trhe same in profile, but each one ended up looking different. The barrel is a Colrain and I trimmed off three and a half inches, filed the end as best I could and used a nail set to put in the circles around the face of the barrel.
The barrel was aged in this fashion: I draw filed the barrel, then I filed the edges of the flats, then I used a palm sander and sanded down the barrel. Sometimes I use a small hammer to dent the edges of the flats, I then applied cold blue, hung the barrel upside down on a fence (not sure if the fence adds anything, but I have one so I use it) and in about four days it was rusty. I ioled the barrel and caarded (gently) with 0000 steel wool. I made sure that any engraving (my name) was installed befor I started the aging process. As time goes on the barrel will take on a better patina.
I'm not sure oif this is the 'correct' way to do this, but it's what I do, as I have not had anybody teach or show me the 'correct' way to do this (if there is such a thing as a correct way)