Digging through my deeper parts box, I ran across a new old stock .45 ACP cylinder likely from a 1955.
Measuring the throats, they seem to be 0.4534, more or less. I'm using inexpensive calipers, so I only assume they're close.
All of my different bullets drop right through the throats without even slowing down, these being mostly coated SnS and Blue Bullets and the like.
It's been a while since I've looked at the subject, but I'm guessing this cylinder is pretty near useless, in terms of accuracy. Or am I remembering wrongly?

That seems about right. You might be confusing
it with some 45 long colt cylinders which are
known for having large throats.

Your cyl is probably useful. .4534 is probably pretty close to normal for .45 acp S&W cylinders. Some .45 Colt cylinders, including some S&Ws, have real oversized throats as large as .457.

Yeah, I forgot to add, I once had a .45 Colt one with giant throats. Never did find a bullet in my inventory that it would shoot straight.
A shame, it was a beautiful gun.

Better than chamber throats that are too small. Although tight throats can be reamed to proper size.

__________________
Jim
S&WCA #819

I have a notion to see about getting my beloved old Highway Patrolman done over to .45. Need another big-bore and this is still my favorite revolver ever.
There'll be enough .357s left in there to hold me.

Me too. So I simply added to my inventory. A supply of bigger boolits turned it into a tack driver.

Gypsm Jim, no doubt that's the right thing to do.
The problem was, at the time, that I was shooting boxcar-fulls of .45 ACP SnS .452" as a heavy USPSA competitor and couldn't be bothered to putz with odd bullets.
Today might be a different story, but, oh, well.

I have found plated bullets such as Berry’s to be a big help accuracy wise with oversized cylinder throats.

Slug your barrel. Likewise slug all 6 cylinders. As long as the bore is smaller than your cylinder your gun will shoot okay. If the difference is only a little from cylinder to bore it may shoot great. Important to find cast lead bullets to fit the barrel, especially if your bore is .453 or 454. Your accuracy will markedly improve.

I often size my 1917 S&W and 1917 Colt bullets to .454" to fit the throats, although both shoot well enough with commercially cast bullets of .452" diameter.

__________________
Keep your powder dry.

I just converted a 1917 to 44 special because the 45acp cylinder had throats of .457! I was getting key holes at 25 yards and at ten yards you could see the bulletin strikes were off kilter. I went from shooting patterns with the 45acp to groups under 3” at 25 yards with the 44 conversion.

I agree. I strive to minimize my inventory as well. Turned out that my new fat boolits worked better in ALL my other guns of "45" caliber, so I got rid of all the skinny ones.