Just curious Driftwood, have you ever had an end shake issue with an SAA?.
This Uberti I have has the cylinder face contacting the rear of the barrel if I point the barrel down.
To me this is as bad as it gets. But my experience is based on Rugers or S&W D A revolvers.
I am curious if the endshake was there when the revolver was new, or if it happened after the revolver went back for service.
The cylinder certainly should not be rubbing against the rear of the forcing cone, and your photo shows it is doing so rather badly, with the blue wearing off the front of the cylinder.
Endshake is defined as the cylinder being able to slide forward and back along the cylinder pin.
A tiny bit of endshake is almost unavoidable with many revolvers. I have a 2nd Gen Colt that I bought used about 20 years ago. It needed a little bit of smith work when I bought it, and the smith pointed out to me that the cylinder had some endshake. He also told me that endshake tends to get worse after the revolver has been fired many, many times. Probably from the cylinder being able to pound backwards against the frame. I never did anything about the endshake and I have been firing full house Black Powder 45 Colt loads in it for twenty years now. If the endshake has gotten worse, I have not noticed. Of course I did not note down how much play there was 20 years ago, so I have nothing to compare it to today.
The shims sold for endshake are placed over the cylinder pin in front of the bushing on the front of the cylinder. They eliminate the cylinder sliding back and forth and also serve to maximize the barrel/cylinder gap. Let's say the gap was .006 with cylinder shoved all the way forward, and .010 with the cylinder shoved all the way back. That means there is .004 of endshake. Placing two .002 shims over the cylinder pin in front of the bushing will stop the cylinder from sliding back and forth, and leave a .010 b/c gap. A little bit wide, but not the end of the world.
However endshake should not be so bad that the cylinder is rubbing on the rear of the barrel forcing cone as yours is. Do you have some feeler gauges? You can determine how much endshake you have by measuring the b/c gap with the cylinder all the way forward and all the way back.
I have never had occasion to use shims, I think I have some somewhere that I bought for that Colt. Just never used them because it seemed to me that it would be easy to lose them every time I took the cylinder out to clean the gun.
If you read Kuhnhausen's book he says endshake should be zero, but personally I would not sweat .001 or .002 of endshake. Maybe later today I will measure the endshake on that Colt. I will let you know how much it is if I do.