I have several barrels for one of my 6PPCs, and they were all chambered by the same smith, with my reamer. The difference in headspace is a maximum of .001. I interchange brass between them, with no problem. I do keep brass in sets so that all the cases in a set will be similarly work hardened. This keeps shoulder bump at a given die setting consistent. Another thing that I sort by, within groups of cases is the amount of force required to seat bullets. If a case feel different from others, I will use it for fouling shots, or if there are a number that are similar, I will use them together to shoot a group. One thing that I have found, in all calibers, is that if bolt close feel is different, within a group, that accuracy will be degraded. Because I have sets of cases that have different amounts of work hardening, I take care to set my FL die each time that I start a loading/shooting session, removing the die when I pack up to go home. (I load at the range for my PPCs.) A couple of times I have forgotten to back off my die, and reset it, when working with newly fire formed cases, and ended up pushing the shoulders of a couple of cases back .0035, instead of .001 or less. This is because the die had been set for old brass, that had more spring back. After that, I started taking the die out of the press, so that I would have to reset it the next time, avoiding the problem. I should add that it does not take me very long to set my die. I have a Lee lock ring locked on the die by a Hornady ring above it, and I know where the gap in the Hornady ring should be in relation to the press, for various settings.This way, all I have to do is to screw the die down till the O ring on the bottom of the Lee ring makes contact, advance the die slightly till the gap in the Hornady is a my longest setting, and start sizing and checking my first case, using a gauge that came with my Harrell's die. It only takes a minute or so. Also, from time to time, during the day, I will check bump, because I know that as cases harden, the die will have to be reset (very slightly) to maintain the same bump. I have a friend that tends to look at setting his dies like it is a major event, and if the setting is a static thing. I take a different approach, using shoulder bump as my guide, making changes as needed to get what I am looking for. One thing that I should mention is that I leave my cases unsized between shooting sessions, and fire and load them in rotation. I keep them in ammo boxes in the same order that I put them in the loading block, and work through the set from beginning to end,and then back to the first one. Also, if a case falls so that its neck is dented, I use it for a fouling shot the next time, because experience has taught me that even if I work out the dent, and resize the case, the shot will not go where it would have. If the neck is bent in a way that will not come out even, after firing and sizing, I throw it away. Of course this is more of a problem with cases that have been turned for my .262 chamber neck, which are all less than .0085 in thickness. What I really need to do is to put a small thin rug in my kit, and place it so that cases that fall hit it, instead of the concrete.