Howdy
Usta be that the advantage to owning a revolver like a Ruger with two cylinders, 45 Colt and 45 ACP, was that there was lots of relatively inexpensive 45 ACP ammunition on the market, usually less expensive than 45 Colt ammo.
HOWEVER, I am talking about a strong, modern revolver designed to take modern ammunition pressures. SAAMI Max pressure for 45 Colt is 14,000 psi, SAAMI Max pressure for 45 ACP is 21,000 psi.
That is what Kirst is warning you about. His cylinders, and those designed by Kenny Howell and marketed by Taylors are not designed for those pressures. Those guys who tell you they are firing factory FMJ ammo out of a Kirst cylinder are doing it completely against the recommendation of the manufacturer. They are playing with fire.
As stated, 'Ammunition: The Kirst Konverter™ is designed to be used in steel framed revolvers with black powder or equivalent cartridges, ‘Cowboy Loads’, as provided by manufacturers such as: Ten-X, Black Hills, Ultra Max, 3D, PMC, Zero, Winchester, Cabela’s. Cowboy ammunition must, by SASS (Single Action Shooting Society) definition, be loaded with lead bullets with a low-pressure, powder charge that DOES NOT EXCEED 1000 FEET PER SECOND VELOCITY.'
That is a direct quote. Believe it.
Now here is the rub. There are no official SAAMI definitions of Cowboy Loads. No Max pressure guidelines, nothing. It is nice to talk about a max of 1000 fps, but velocity does not define pressure. Pressure defines pressure. A 200 grain bullet moving at 1000 fps is going to have a very different pressure behind it than a 250 grain bullet moving at 1000 fps. And it is pressure that is important, not velocity, in regard to not blowing up guns.
So if you ain't going to be reloading, but are trying to find factory ammo for a Kirst 45 ACP cylinder, you really ought to consider buying one for 45 Colt and buying factory Cowboy loads. Yes they are expensive and hard to find these days, and no their pressure is not well defined, but they will not hurt the gun or the cylinder.
Or what you really ought to start doing is to start reloading.
P.S. I shoot a pair of 1858 Remmies with R&D cylinders. I usually shoot them with 45 Schofield Black Powder loads, and yes, I load them myself.