The problem is you that believe it is so important have probably not actually tested your theory's out. Ok so Colt supposedly actually custom fit the arbor to the well end (which I seriously doubt) in their production guns, that does not prove a thing in actual accuracy comparison.
My personal experience with the short arbor was not so much the ‘accuracy’, as it was to functionality. I was using Colt clones in SASS a while back, and at times reloads were required during completion while on the clock. Tried two methods, pre made paper cartridges or a cylinder swap. The paper cartridge reload was doable, though time consuming (remember, this is a time based competition, and many times someone shooting an open top or a Remington NMA would be the only one doing so), plus the reload had to be done without breaking any of the muzzle sweeping rules. The cylinder swap was potentially much easier and definitely quicker. The problem with the short arbor was the tendency to drive the wedge in too far, closing the cylinder gap and jamming the gun. You had to check and make sure the cylinder was moving freely and adjust the wedge before capping. May not seem like a big deal, but you were on the clock. Some guns would seem to hang up with just firm thumb pressure. With the arbor the correct length, you could not close up that cylinder gap with a mallet. A quick bump with the pummel of your knife handle and you were good to go.
As far as accuracy, as you drove in the wedge, you could raise or lower the POI depending on how far you drove it in. In SASS it didn’t really matter as we were trying to ring relatively large steel targets at close range.
My guess is Uberti found it unnecessary and much easier to produce.
The most recent Uberti Walker I worked on had an arbor about an eighth of an inch too short. Definitely an acceptable tolerance if I were building a wooden stockade fence in the the back yard...... but for a handgun?
You can drop washers down until it fits snugly but still will never be exact.
Agree. What we did was confirm measurements with shims until the cylinder gap was correct, then made a single piece the correct size and pressed/Loctited into the barrel assembly.
I don't have a vintage Colt to actually check but my guess is they don't bottom out with any consistency either especially as the gun gets some wear on it.
We checked two different vintage Colts (both with all matching serial numbers) and found both to put .003”/.005” pre-load on the bottom of the frame. To confirm we used shims (.002” to .006”) in the hole in the barrel assembly to find when the barrel and frame made contact. Do not know if that is how the guns left the factory, but that is how the were found 150 plus years later.
Below is a photo of a Pietta (sold by Navy Arms) before the change to CNC machining. Arbor is about a .100” short, similar to the latest Ubertis I have seen.
Not an expert. Just stating my observations and opinion.
