Now I just saw something from Bowen that had a single action ruger 357 converted to a 5-shot 44 mag or 41 mag. I think I have also seen something by a custom company about a gp100 357/44 spec conversion but not so sure about that.
If it is not possible then how did they do it? The size of the single action and double action cylinders have to be pretty close, don't they??
If for some reason they can't do 44 mag, I would still like to see a 41 mag 5-shot.
AS to why it can't be done.... (dimensions taken from my own Ruger Security-Six)
The 357 has a wall thickness on the outside of the cylinder of only .085". It is there to handle the 35000 psi of the 357 mag
The 44 Mag has .077" more diameter on its case and another .060 diameter on its rim.
That means that the cylinder would be reamed .039" per side leaving .046" of wall to take the extra pressure of the 44 over the 357.
The rim of the 44 is .037" larger (from the centerline) meaning that you have .009" from the rim to the outside of the cylinder.
The center part of the cylinder with the star on it would have to be cut away for the rims or the rims would have to be trimmed.
That is why the 44 mags have cylinder diameters that are larger in diameter than the 357's.
The frames are taller so that the barrel can be mounted higher allowing the location of the center of the cartridge (and bore) to be farther from the center of the cylinder pin.
The dimensions of cartridges are the industry standard sizes for the cartridges and do not include the extra .002" - .004" of the chambers diameters. If I added the minimum of .002" of the chambers then it would further reduce the wall thickness to only .044". I doubt that even the Ruger could withstand the 36000 psi of the 44 mag with cylinder walls only .044". The 41 mag is only .005" smaller diameter than the 44 so when you divide that by 2 you would end up with a wall thickness of .0465" - probably not enough to handle the 36000 psi either.
edit - even a five shot 41 or 44 mag would need the larger cylinder - there just isn't enough metal in the 357 mag cylinder.
If you cut the frame and welded it to support a larger cylinder moving the barrel up to align with a larger custom cylinder then you could do it.
Why not just use a larger frame revolver in the first place?