I think the evil of MIM is overstated.
This.
In the early days, the quality was hit and miss. Good MIM can be very good. Bad MIM is worse than junk. The problem is that, short of an obvious defect on the surface, it's impossible to determine by eyeballin' it.
A little story.
A friend of mine was concerned with the MIM sear and disconnect in his early "Billboard" 1991A1 so he bought the best stuff and had me swap it out for him, despite my telling him that it probably wasn't an issue. He was adamant, so we proceeded.
In an attempt to allay his fears, I laid the Colt OEM sear on an anvil concave side down and whacked it a few times with a 4-ounce hammer. It didn't shatter, and when I reinstalled it into his pistol and test-fired it. The trigger pull was a little rougher, but it functioned.
It would be hard to imagine the sear suffering that much stress in a hundred thousand normal cycles.
Then, I clamped the disconnect in a vise and whacked it briskly with the same hammer. It bent at about 30 degrees, but it didn't snap like he expected it to.
I have two early 1991A1 Colts that had MIM sears and disconnects as OEM. The pistols are approaching...collectively...400,000 rounds about evenly split. One is still running on the original sear and disconnect. The other on the original sear. I replaced the disconnect at about 75,000 rounds...not because it failed...but because it looked a little worn and I wanted to nip any future problems in the bud.
Colt apparently found a good vendor for its small parts, and stuck with'em. The only MIM part that didn't turn out well for Colt was its experiment with MIM extractors. As far as I know, they're the only manufacturer that gave it a try with extractors. They learned their lesson and went back to barstock extractors shortly after.
In the beginning, Kimber's MIM parts were good...then it went wrong for some reason. I understand that they've since corrected that, and have found a good vendor.
There are some parts that MIM is well suited for...and some that aren't. Most of the horror stories come from the days when MIM was in its infancy. It's improved a lot over the last 20-odd years.
