I had Cylinder and Slide Shop do the same to my stainless Bearcat. After I could actually see the sights, I found out how accurate the gun actually is.
My .45 Colt NMBH was made around 2000. The chamber throats were tight and in several shapes other than cylindrical. Fortunately they were tight enough that a reamer could clean up an S shaped or tapered or oval, or whatever shaped. After reaming, they shot much better.
My Marlin 39A is 60 yrs. old and wears an old Redfield receiver sight. I don't think I have changed the sight settings in years, although I finally got around to replacing the bead front sight with a serrated ramp, which I favor.
I picked up a used Marlin 336 and mounted a Williams Foolproof...
I have trouble believing that using the short .45 ACP in a long .45 Colt chamber is conducive to good accuracy. It may be nice to have the option of shooting 45 ACP in a .45 Colt Redhawk, but I would expect much better accuracy in a .45 ACP chambered revolver, like a S&W 625 or the .45 ACP...
I find the "other" cylinder very useful. For mild range loads, I prefer to use .45 AR brass. I had the cylinder trimmed to headspace .45 AR. I use the same ammo in my NMBH and S&W 625.
You can get 9mm barrels that are supposed to work in the .357 SIG slides, or you can go whole hog and get the 9mm conversion which includes slide, barrel and recoil spring. My SIG 229 was originally a .40 S&W. I got the 9mm conversion and that is how I usually shoot it
Got everything covered except the 12 ga. pump. I'm not a pump guy; I like my Browning Auto 5.
Other than a matter of personal preference on the shotgun, the list is reasonable.
I have a stainless .45 Bisley and had trouble with the factory grips. I found, through trial and error, that smooth Eagle Gunfighter work well for me particularly when shooting heavy loads.
Cylinders typically aren't necessarily drop-in. It may require fitting. If you can get one, it is a great pick-up. I mostly use my .45 Colt NMBHs with .45 ACP cylinders, converted to also allow .45 AR, which is what I mostly use.
I remember several stories from Keith about Smith. I also remember a photo of John Newman, an old time lawman. What I remember most about the photo was the eyes of Newman, how they seemed to jump off the page. He was not a young man in the photo, but he looked like a very tough SOB.