Wever, just a thought: do you measure each of your cartridge OAL after seating or do you seat one, and having determined that is 0.05" from the lands, just continue to seat the rest and not measure?
Barnes may have improved, I don't know because I don't reload Barnes, but when I did years ago in my .270 Win, I found significant variation in the final measurement and I thought it is explained by a changing bullet ogive position even in the same box of a given lot number. I chalked it up to a possible idiosyncrasy seen with pure copper bullets. That also explained to me why Barnes, at that time, suggested you should not seat the bullet any closer than 0.05," but again, this was just me brainstorming.
Thus if you didn't measure each one, maybe some were seated right out to the lands and this increased your pressure. The same may be true of the Swift Sirrocco bullets since you are starting there at 0.03".
I routinely measure every seated round. Even if the bullet is not the problem, differences in neck thickness can change the seated depth. If your dummy round is made with an unfired case, and you reload a round into a case fired multiple times that has been routinely trimmed and chamfered with a variation in enthusiasm from time to time, the internal diameter of the neck can be thicker and your seated round will be longer.
Just a thought.