The 1911 I'm on now, has a few special challenges. One is, two barrels. I mean, you can bing bang boom-fit a barrel and it will be fine. I just don't do it that way, doing it my way is kinda tedious but it's what satisfies me. If doing it for two separate guns, let's say it's "X". doing two barrels for the same gun, it's X times two.
And before I even got to that, well, I ordered Kart barrels of course, a bull barrel in Super .38 and one in 9mm. They came in a conical format, which to me is a big no-go. That shape allows the front of the barrel to dip as the slide moves to the rear, which can lead to the rear being biased up and- sometimes-- reliability issues. I sent them back and requested to trade them for the now more common style (I think), a straight cylinder but with clearance on top to allow it to bump up into battery. I was informed Fred thinks that could be detrimental to accuracy; I don't think so----- in a .45 pistol... but then I'm not Fred Kart. So they came a straight cylinder. There is nothing to be done with that other than either turn it into a cone or the other, top-clearance shape:

So, the preferred top clearance it was. The doing of it was not too bad, although the room for error was minimal. I mean a place doing them by the batch, probably no big deal. For me the setup was long and arduous. Then came the fluting, using the same setup more or less. But then another biggie is trying to get two barrels pointed in the same direction. This involved a lot of back and forth, not fitting one and then matching the fit on the other as much as creeping up on the fit one, then the other, then back, then back again…. Can you really get two barrels to shoot to the same POI at 28 yards? In the several, but not many, that I have done, I’ve had pretty good luck. Better I think than just fitting one and then the other, independently and hoping for the best. Some barrels, or barrel fits, in .45, will shoot mild 155’s, mid-range 200’s and +P 230 JHP’s to POI’s that are within two inches or so at 28, that’s always nice. Now we’re doubling that requirement, no, that hope, that 115 FMJ’s and 147 JHP’s in 9mm, and .38 ACP’s and .38 Super +P’s, shoot to the same POI. Fixed sights on the gun—gotta try.
Special challenge #2, Conamyds on the trigger. Done, came out nice. That’s the first time I’ve done them on a trigger.
#3, make the magwell .250 thick instead of .300. Not sure why that request but I thought, why not? Since I make them all from scratch anyway, I don’t think there’s an issue. I’ve been making magwells out of the same block of Crucible prehard 4130 (or is it 4140, not sure now) steel for many, many years—there are several left in this chunk. I thought it was cool to use Crucible steel for them because at the time I got it, Crucible was a part of Colt Industries.