Ok
Headed to gunbroker to look a S&W 25s....
Thanks guys.
I would recommend looking only for S&W 45 LC dash seven or higher.
This was the first year, may have been the first run, which S&W cut the chamber throats to 0.452:
Before 1989, S&W M25's in 45 LC had larger chamber mouths. Which shot poorly with 0.452 bullets. Lead bullets of diameter 0.452 excessively leaded, jacked 0.452 bullets shot better than cast, but were not exactly tack drivers.
my phone call conversation notes with Doug Brassard of S&W Customer Service:
25 March 1991
I asked Doug about the chamber dimensions that were allowable for the 45 Colt. This was in reference to a discussion I had with Lee Precision about their carbide crimp die sizing all the 45 Colt cases with .454 diameter bullets. Doug said that Smith and Wesson belongs to SAAMMI and receives their specifications. Only American ammo and gun manufacturers belong to SAAMMI. SAAMMI allows a rear diameter of .4862 nominal plus .004 and .4806 plus .004 for front of the 45 Colt chamber. When I asked him about the 45 Colt ball chamber throat diameters he said that they used to be .4545 to .4565 but now they were .452 . Smith and Wesson has its own standards for the barrel dimensions for the 45 Colt and they are : one turn in 20, 5 groove, lands .444 -0.0 + .0012, groove .451 - 0.0 + .0017. For the 45 ACP it is a 6 groove barrel, 1 turn in 15 inches, lands of .443 -0.0 +.0012 and grooves of .450 -0.0 and +.0017. Interestingly enough the SAAMMI specifications for 45 ACP lead bullets and jacketed bullets are different. Jacketed specs are .452 -.003 and lead bullets .453 -.003.
If you can find commercial cast 0.454 inch diameter lead bullets, using the bigger bullets will tighten the groups of older S&W's considerably. When I finally found 0.454 diameter commercial cast lead bullets, I had divested myself of my older S&W 25 in 45 LC, but I found the larger diameter bullets shot very well in this 25-7. I guess being a little large for the chamber mouth is not as problematic as being a little too small.
Anyway, I recommend trying to find the later, dash 7 or higher, 45LC's, as most 45 caliber bullets are 0.452 in diameter.