rechambering 44 mag cylinder to 45ACP

[Fireforger]

Just need some thoughts on rechambering a .44 magnum single action revolver cylinder to .45ACP (to use in a revolver already chambered in .45 Colt). I know this can be done but can it be done safely, considering .035" difference in rim diameters (but it does look like the ACP case head will be adequately contained in the chamber walls)? Just looking for options with an extra cylinder. Thanks.

 

[BBBBill]

Is that same gun already available as a 45 ACP (Ruger Super Blackhawk, etc)?
Are you trying to adapt a cylinder from another manufacturer?
What is the overall diameter of the cylinder in question? Same as the current cylinder?
What is the overall length of the cylinder in question? Same as the current cylinder?
What is the chamber wall thickness at the thinnest point before reaming to 45 ACP?
Those are just a few of the things you must address. Given the tremendous difference in pressures between the 44 Mag and 45 ACP, I would think that it could be done based on that alone, but a lot of measuring and thought would have to go into the decision process with both cylinders in hand.
Why do you need two cylinders in 45 ACP for the same revolver?

 

[NCsmitty]

Why do you need two cylinders in 45 ACP for the same revolver?

I believe he mentioned that the other revolver is a 45 Colt. He's looking for a combo setup and it may be feasible if both are the same model frame.
With no pertinent information, it's a guessing game at best.


NCsmitty

 

[Fireforger]

Gun is a Virginian Dragoon in .45 Colt. I have an extra cylinder for one in .44 mag. Just looking for a nice convertible. The cylinder is plenty big enough - I'm just looking for thoughts about the little bit of brass that would be unsupported at the .45ACP rim (or case head) if a .44 mag cylinder is rebored (the cylinder is rebated for the .44 case so that probably helps a little). More thoughts?

 

[BBBBill]

I suppose you are saying that the cylinder is recessed so that the case heads are enclosed on the sides as in the old S&W revos. That has zero effect on headspace or case support. It is a cosmetically desirable feature for some folks who swoon over such examples of gun building. S&W eliminated that as a cost saving measure. Guns cut for moon clips have more cut away for clip clearance.

Is the new cylinder the same outside diameter as the existing cylinder? If it is substantially smaller, that would be a bad sign.

Key to all of this is to, first, determine if the cylinder is adequate in diameter/cylinder wall thickness and can be properly fit to the frame. You might have to fit a new base pin bushing to help set endshake and headspace. If you can't buy one, a machinist can turn one easily enough. Once the cylinder is properly fit, then and only then can you proceed with reaming the chambers and throats to 45 dimensions. The proper reamer will be revolver specific. Do not use one made for an automatic. They are different.

The 45 headspaces off the case mouth. The rim is .049"-.010" (.039"-.049") thick. Rim diameter is .480"-.010" (.470"-.480"). Case diameter is .476" at the base.
The .44 Magnum headspaces off the rim. The rim is .060"-.011" (.049"-.060") thick. Rim diameter is .514"-.010 (.504"-.514"). Case diameter is .457" at the base. Headspace dimension is .060"-.070" on 44 Mag revos.

So, based on the fit of your new cylinder to the frame, ream the chambers to minimum headspace for 45 ACP and you are left with .011" (best case) to .031" (worst case) of case exposure ahead of the rim. If you were to ream to max headspace (why?), then add .020" to those measurements. You would likely start having ignition problems at that point. As for the case exposure, a standard GI issue 45 has more than that under normal circumstances. The safe unsupported case exposure on the 45ACP is .250"-.260". That is in a gun that can have wildly different static and dynamic headspace.

You might be able to use moon clips with this depending on just how close in dimension your cylinder is to the S&W N frame 45ACP.

These are just general thoughts in no specific order. The order of work will be determined by what you have and where you're going, but must start with pre-fitting of the cylinder and measurements.

Lots of measuring. Lots....

 

[Old Fuff]

You might be able to use moon clips with this depending on just how close in dimension your cylinder is to the S&W N frame 45ACP.

The revolver in question (a Virginian Dragoon) is a more-or-less copy of Colt's Single Action Army. Half or full moon clips won't work with the revolver's individual round/side rod loading system.

A greater problem is that the .44 Mangum chamber (not cartridge) diameter will be too large and too long vs. the .45 ACP, that should have a .452" throat. That's hard too do if the original round's body diameter was .457" and the chamber is even bigger.

 

[rcmodel]

This is exactly right.

You can still do it though, by starting with a .357 Magnum cylinder.

rc

 

[BBBBill]

The revolver in question (a Virginian Dragoon) is a more-or-less copy of Colt's Single Action Army. Half or full moon clips won't work with the revolver's individual round/side rod loading system.

A greater problem is that the .44 Mangum chamber (not cartridge) diameter will be too large and too long vs. the .45 ACP, that should have a .452" throat. That's hard too do if the original round's body diameter was .457" and the chamber is even bigger.

Yep. I wasn't thinking about that part. T mentally shifted to swing out cylinders. Doh!
I did consider the throat. I just discounted it because I interpreted his question to be about something to play with a bit as opposed to a serious use piece. That was a bad assumption. Large throats would be detrimental to accuracy. The 357 cylinder is the better idea by far.

 

[Fireforger]

I didn't think about the large throat issue so glad I asked (but I do agree that the little bit of unsupported brass was not going to be an issue). I do have a .357 magnum cylinder but it fits my other Virginian Dragoon which also has a .357/.44 Bain & Davis interchangeable cylinder (chambered by Hamilton Bowen). That gun is scoped (barrel mounted) and is one of my hunting handguns. And yes, I meant to say recessed, not rebated. Not sure where that came from. Thanks for the discussion.