Jim
I've got two model 25s, one four inch, one six inch, one 625 with a five inch, one Colt Anaconda six inch and a Ruger Blackhawk 4 5/8ths.
Time was I'd shoot tens of thousands of rounds through my original six inch Model 25 every year. After putting 50,000 to 60,000 of my recipe through it, I sent it back to S&W for a new barrel and cylinder, and a patridge front sight. This time the old gun has a 4 inch .452 barrel and .453-.454 cylinder mouths.
All of my 45 Colts use the same bullet, Saeco 255 grain SWC bullet from wheel weights, sized to .454, lubed with LBT ahead of 9.5 grains of Unique. The Anaconda gets a special diet for hunting, of 300 grain Saeco gas checked SWC, sized .454 ahead of 20 grains of H110.
Every time I try .452 diameter cast bullets I get leading, when I go back to .454 I don't get leading and I truely hate leading.
One important destinction with all of my 45 Colts have had their barrels hand lapped. No constrictions in any of my barrels.
I could add that my shooting partner has three 45 Colts and a 454 Casull. They all like the .454 size bullet and none of them lead.
Have fun the 45 Colt is a wonderful caliber.
Jim

Thanks to all for the info.

I already have a Blackhawk Bisley .45 Colt � this was bought about 2001 during that special run for AccuSports in Ohio � stainless, Bisley grip, 5 �� barrel with adjustable sights. Throats are a bit too tight, probably around .451 so it doesn�t handle cast bullets all that great but it will group Hornady 250 XTP�s with a MV of around 1300 fps into an honest � � at 25 yards. I am loathe to open the throats � probably won�t hurt but one hates to do anything that might mess with groups like that.

Anyway � it�s a bit heavy at 46 ounces and I was looking for a lighter gun. I have that 4� M586 and there are no flies on the .357 Magnum, but more and more I like big bullets at moderate speeds. I�ve shot .44 Magnums for, geez, about 30 years, but even then I�d say 99% of my loads shot a 215 or 240 grain bullet right around 1000 fps. Low muzzle blast, recoil is not bad, and they just flat get the job done. Sold the last of my .44�s when I got that Ruger .45 Bisley. I sure like Ruger Blackhawks, have owned a slew of them, but also have a �thing� for S&W revolvers in the 4� persuasion, so the 2004 Mountain Gun in blue with wood grips is just calling to me a bit more than I can resist.

I think you are quite correct and very wise to limit the loads for a Model 25 S&W. The cylinders of thease are NOT heat-treated to the same strength as their magnum cylinders. In addition, just take a look at how thin the chamber walls are, particularly in the area of the locking bolt cuts!!

The Lyman-Keith 454424 cast to around 260 grains and loaded to the 900-1000 FPS level is a great killer without being hotrodded!!