I've been looking online for a model of 1955 up through 25-2s.
What's the scoop on throat sizes and shooting decent groups with these? (I reload)
I'm guessing they're anywhere from 452-456?
Will ball ammo shoot better in the guns with larger throats?

I've had a 25-2 for a long time. I think it was manufactured in the -'70s. I shoot .452" cast bullets in it. I don't know what the chamber throats measure, but it's likely my most accurate revolver. I'd certainly buy another if I found one at a good price.

Jacketed bullets are usually more forgiving of oversized throats than cast bullets. I may have fired jacketed bullets in my gun; if so, it was very few. Don't recall accuracy.

If you find one of these guns with oversize chamber throats, it's not the problem many perceive it to be, but you'll have to buy or make cast bullets that closely match or very slightly exceed the chamber throat diameter. This could require a custom mould and size die, but that's a one time expense. With bullets of the proper diameter, such a gun should shoot very accurately. I would certainly find it worth the trouble.

I purchased my 25-5 .45 Colt new around 1980. It has huge chamber throats. I think they are .456" or .457". I had a Lyman #454424 mould from the '50s or '60s that cast bullets of the right diameter. I run them through a .45-70 bullet sizing / lubricating die so they only get lubricated, not sized. Works well. Use Winchester brass and you won't get a case bulge. Loaded cartridges chamber easily.

.45 ACP or Auto Rim should be no different.

That's good to know.I do have a supply of 452s and 454s due to a colt saa I picked up about 10 yrs ago.The 454s work nicely in it

I have a Model of 1955 (pre-25) that shoots as well as my Les Baer M1911A1 that I use for NRA bullseye matches, using a 200 grain lead SWC (.452) and 3.6 grains of Bullseye. Don't use rimmed cases or half moon clips; just poke out the ACP cases with a pencil.

Most of the acp guns had decent sized throats. The 45 colt guns not so much until part way through the 25-5 gun run.

Years ago I remember being at the range with somebody who had a Model 25. He stated that not only were the cylinder throats large, but one of them he referred to as being "egg-shaped." He said he sent it back to Smith & Wesson and it put a new cylinder in the gun that was much more in standard. I remember that I belonged to that club in the late 1970's and early 1980's so you can use that to determine what ownership group was in charge of S&W back then.