Notes on two .45 ACP cylinders..

I see the question raised often about buying .45 ACP cylinders from one source or another, and whether they might fit, either as a drop-in or with slight fitting. So, I put the calipers on the two I have, and tried them in my Vaquero.

My first .45 Blackhawk is a 7 1/2" gun bought in 1987, and returned to Ruger for the ACP cylinder. The second gun is a 4 5/8" gun bought in 2000, and was a purchased as a convertible. The Vaquero was purchased in 1996.

The overall length (OAL) of the 7 1/2" gun's cylinder 1.959", ratchet to bushing. The 4 5/8" gun's cylinder is 1.980" OAL.

Putting the 7 1/2" gun's cylinder in the Vaquero, it fit, and was able to seat the base pin. The cylinder functioned and locked up properly, but there was nearly .20" gap between the bushing and cylinder frame. And the face of the cylinder rubbed against the barrel stub.

The 4 5/8" gun's cylinder dropped in as if made for the gun. I did not measure barrel/cylinder gap, but it looked proper, and the gun seemed to function correctly.

So, will an aftermarket cylinder be a drop-in fit? Maybe, maybe not.

Bob Wright

As you say it can, will and did "drop in" does that make it right? no, that much of a gap is bad, headspace is 'wrong' can get misfires, etc,the stub ( gas seal) is supposed to ride on the frame,NOT rub up against the barrel,,,,change to forward or rear ward movement and then the timing may also change, not align properly with the bore to cylinder.lock up or not, etc.,,,,,,,,,,,proper fitting (safety) is of the utmost, no sense in asking for a "problem" when it comes to actually firing off all the rounds.........
as for "aftermarket" cylinders, if the size is the same, it should and could work,after all they are made ,fitted for , the original gun that it ( cylinder) was installed in...............

rugerguy said:

As you say it can, will and did "drop in" does that make it right? no, that much of a gap is bad, headspace is 'wrong' can get misfires, etc,the stub ( gas seal) is supposed to ride on the frame,NOT rub up against the barrel,,,,

Click to expand...

To clarify our terms here, the "stub" to which I referred was the barrel stub, that part of the barrel that protrudes into the cylinder window.

And what you are calling the "gas seal" is what I termed the "bushing."

The bushing is fixed on the Ruger, removeable on Colt revolvers, and most clones.


As I said, I checked only for fit and function, did not measure headspace nor barrel/cylinder gap.


Bob Wright

Just read this thread and the other about 45 "auxiliary cylinders" the only dual cylinder revolvers I have are single sixes. I tried swapping them around and one magnum cylinder will work in my bisley single six. BUT, this single six was not shipped with a 22 magnum cylinder. Does that mean i can or cannot use the mag cylinder in the bisley? Sorry for being so wordy... The fit and function is spot on.

And another question, how are the cylipfitted to a gun? If it is the correct length for the gun but won't index, how are they made to be timed properly? I've wondered about this for a long time now.

Kevin said:

Just read this thread and the other about 45 "auxiliary cylinders" the only dual cylinder revolvers I have are single sixes. I tried swapping them around and one magnum cylinder will work in my bisley single six. BUT, this single six was not shipped with a 22 magnum cylinder. Does that mean i can or cannot use the mag cylinder in the bisley? Sorry for being so wordy... The fit and function is spot on.

And another question, how are the cylipfitted to a gun? If it is the correct length for the gun but won't index, how are they made to be timed properly? I've wondered about this for a long time now.

Click to expand...

I installed a mag cylinder in my Bisley Single Six and it works perfectly. I got lucky on the length with that one, but when did the same on my 45 Colt Bisley with a 45 acp cylinder I had to stone off about .005" to make it fit. No big deal. It also works perfectly. If you are going to do a cylinder conversion just make sure the "new" cylinder is at least as long as the original as you can remove material easily but cannot add it without a great deal of work.

Not sure what you are asking in your other question. If a cylinder is the correct length and diameter and has the same number of holes it should index and "time" just fine.

Thanks for the explanation s4s4u. It helped clear up some stuff. So it sounds like the overall length is most important. Assuming the caliber is able to shoot in the gun of course.

I forget the bore dimensions off hand, but the .22 r.f. and the .22 WMR have slightly different bore diameters, the .22 WMR being slightly larger. The .22 L.R. works when fired in a WMR bore, but the .22 WMR doesn't work so well when fired in a .22 L.R. bore.

In short, a true .22 L.R./.22 WMR will have the bore suited to the .22 WMR.

In considering custom cylinders, that is, using a cylinder of a caliber smaller than the intended host revolver, both OAL and cylinder length must be considered. By cylinder length I refer to the length exclusive of the ratchet and bushing. Ruger has purposely made cylinders of length to preclude their use in the "wrong" gun. That is, a .44 Magnum cylinder cannot be installed in a .45 Colt revolver. Same with .357 Magnum cylinders. Thus a person could not put a .44 Cylinder into his .357 Magnum revolver inadvertently. This does not mean they cannot be made to fit, however.

I post this as there are those who may buy a .357 cylinder with the idea of boring it to some wildcat caliber, fr example.

Bob Wright

Bob Wright said:

Thus a person could not put a .44 Cylinder into his .357 Magnum revolver inadvertently.

Click to expand...

If you're bound and determined to screw up, it can be done. Good friend of my Dad and my Dad were shooting one day when the friend managed to chamber a .44Mag round in his .45ACP Blackhawk and make it go bang. Very BANG. No damage to gun or shooter, except dignity and possible laundry issues.