When I took the Colt out to the range the first time, the slide did not return to battery most of the time. I assumed this was just in need of break-in.
But last night I noticed something.
While the gun was disassembled, I dropped a live round into the chamber, and it did not fall in all the way. About 1/8" of the cartridge stood proud of the rear of the barrel. This was a handload I had laying around, made on my Dillon 650.
I started dropping rounds from my ammo cans into the barrel, and sure enough, most of them don't drop in. For comparison, I dropped rounds into my Springfield barrel and every single one drops all the way in with no resistance.
After dropping 1200 rounds by hand into the barrel chamber, I found 98 that slip smoothly into the Colt barrel chamber. The other 1102 rounds drop nicely into the Springfield but stop short of falling into the Colt chamber.
I verified that my resizing die is set correctly.
The only factory ammo I have sitting around is some Remington Golden SAber, and that stuff all drops into the Colt just fine.
So what's going on? Obviously the Colt chamber is a little tighter than the Springfield... but if the Colt cannot eat my reloads then that kills the deal and I will have to dump it.
NOTE: The rounds that do not fit are not measurably thicker than the ones that do, or the factory stuff... meaning, my calipers put all the rounds within one thousandth of an inch of each other, and the caliper does not go any finer than that. But obviously they are thick enough for the Colt chamber to not like them.