Trying to understand this “short arbor” on Uberti revolvers

[RjSixgun]

Just out of curiosity are the wedges tapered on both sides or just one???

 

[Stantheman86]

The source is just General Knowledge from reading countless pages of information since I got my first repro cap and baller in 1992. Also anecdotal evidence from long passed men who used to buy surplused old '60 Armies and '58 Remingtons for $2 at flea markets in the 1950s and shoot them.

They are fitted so that the arbor bottoms out in the hole and the wedge keeps the gun together. The wedge is not designed to take the force of firing. These were expensive guns in their time and each was hand fitted including the wedge. This is simply how they were made. Someone here must have an original Colt open top they can "arbor test" . There need not be a Source, it is a fact.

In the post-Civil War years many 60 Armies were stripped down and "Cleaned and Refurbished " from parts from bins at Arsenals, for reissue on the Frontier so not every original wedge will match.

After I do a quick workout I'll give my Uberti Dragoon the "Arbor Test" and post a pic.

 

[Stantheman86]

My Uberti Dragoon is actually pretty well fitted, the arbor bottoms out just before the barrel assembly hits the frame.

My Uberti London Navy has the arbor hole a little long , the barrel assembly goes just a hair past the frame. I've fired this one quite a bit , no problems. I have about 100 conicals to shoot through it.

Is it that big of a deal to me? Not really. I'm more glad the Dragoon is fitted probably since it takes heavier charges.

I'll see how the 2 Walkers I ordered are when they arrive.

 

[Gun Tramp]

In the post-Civil War years many 60 Armies were stripped down and "Cleaned and Refurbished " from parts from bins at Arsenals, for reissue on the Frontier so not every original wedge will match.

Then ordnance rebuild specifications exist. Somewhere.

 

[jonathan butcher]

As I am clearly thick as a brick, is this where shims are added ? At the bottom of the hole ? Shoud one see daylight between the cylinder and the breech face, or no ?

 

[Phil Coffins]

No. Remove the barrel and the hole that the arbor goes into or the tip of the arbor.

 

[jonathan butcher]

Thank you. And what about the gap between barrel and cylinder- should there be one ideally ?

No. Remove the barrel and the hole that the arbor goes into or the tip of the arbor.

 

[Phil Coffins]

The barrel cylinder gap is measured with the cylinder held back as the hand spring will press the cylinder forward.

 

[M. De Land]

I set mine to .008" (some may prefer a different amount) with the wedge installed and the hammer down. The cylinder will move forward a tiny amount when the gun is cocked and then move back after the shot is fired, but I found the .008" gap in the "resting" position made the gun work just fine and didn't allow the gap to close while cocked to a point where it actually touched the forcing cone.

Edit: Actually, I lied. I just went and measured it and the resting gap is .010". It's been a while since I made this mod, and I'm not sure why the .008" figure popped into my mind when recalling this, but it did. Just for giggles I checked the gap with the hammer cocked and it would just barely let a .006 feeler through. This is a bit larger than most like, but it works for me and makes fowling a non issue.

I am a doubter that arbor depth has much if any effect on accuracy as long as the gap is level and remains consistent at firing. I would rather put a feeler gauge in the gap and push a properly fitting wedge to set the depth. I usually don't do anything but push in the wedge to the same depth each time using the keep screw as the depth gauge on the wedge head, once the depth is determine with a feeler gauge.
Most of the attention is focused on the arbor fit in the well but in reality the wedge fit into its barrel mortises and the lower frame bridge fit in both horizontal and vertical axis have far more effect on accuracy both grouping and centering the shots.
You will notice when using a feeler gauge that the gap will most often be tighter at the top than bottom which is good because these guns were designed with the flexing engineered into them. When the light comes on and the ball or bullet hits the forcing cone I can guarantee the gap is not the same any more. Here is where we want the gap as level as can be on both axis. Wither or not the arbor is bottomed out at this point in the cycle is mute as the whole revolver is flexing into it's stressed, stop positions. You cannot make a machine designed to flex operate into a solid rigid unit by bottoming out the arbor. The end of arbor is not loaded at firing, it is unloaded as the barrel tries to separate from the frame. The wedge, bridge and barrel wedge mortises are. These loaded at firing areas are what is important to accuracy and group positioning. I have never bothered with arbor bottom fit but rather the other areas outlined and the guns have always been more accurate than I can hold for over bench or offhand.

 

[Bad Karma]

I am a doubter that arbor depth has much if any effect on accuracy as long as the gap is level and remains consistent. I would rather put a feeler gauge in the gap and push a properly fitting wedge in each to set the depth.
Most of the attention is focused on the arbor fit in the well but in reality the wedge fit into its barrel mortices and the lower frame bridge fit in both horrizontal and vertical axis have far more effect on accuracy both grouping and centering the shots.
You will notice when using a feeler gauge that the gap will most often be tighter at the top than bottom which is good because these gun were designed with the flexing engineered into them. When the light comes on and the ball or bullet hits the forcing cone I can guarntee the gap is not the same any more. Here is where we want the gap as level as can be on both axis. Wither or not the arbor is bottomed out at this point in the cycle is mute as the whole revolver is flexing into it's stressed, stop positions. You cannot make a machine designed to flex opererate into a solid unit by bottoming out the arbor. The end of arbor is not loaded at firing, it is unloaded as the barrel tries to separate from the frame. The wedge, bridge and barrel wedge mortices are. These loaded areas are what is important to accuracy and group positioning. I have never bothered with arbor bottom fit but rather the other areas outlined and the guns have always been more accurate than I can hold for over bench or offhand.

This has been my experience as well over 50 years of shooting these guns. A couple of years ago I picked up Charles Pates excellent tome on the 1860 Colts New Model Army and happened to see a cross section of the pistol as drawn for the patents office. It does indeed show the arbor bottoming in the arbor recess.

Almost every one of my pistols to that time had the short arbor except for one or two. I have since shimmed one of the replicas so that the arbor bottoms and provides a .003” gap. So far I haven’t seen any difference in accuracy, fouling, ease of assembly, or durability. I do have one pistol that I’ve shot tens of thousands of full power rounds for more than 50 years and it’s still going strong so maybe I just need to conduct a test over a longer term. Maybe another 50 years?

In my opinion, the accuracy limitation of the design comes down to the sights. These are tiny and need to be regulated to the preferred load but they are capable of very fine accuracy nonetheless, providing the light is good and your eyes are up to the task. Mine aren’t what they were back then but nothing else is either...

 

[M. De Land]

As I am clearly thick as a brick, is this where shims are added ? At the bottom of the hole ? Shoud one see daylight between the cylinder and the breech face, or no ?

Putting shims there will block the hand port.

 

[M. De Land]

Putting shims there will block the hand port.

Closing the cylinder gap correctly is quite involved and one should do some reading up on it as well as having proper tooling available before attempting it
There is a lot of simultaneous interface movement going on here with related and linked parts that need to be balanced for peak mechanical function. I've done it by hand but the best and most accurate results were done in my lathe especially when reducing the lower bridge height and keeping it square to the bore. Shortening or lengthening the arbor and inserting a new wedge is not all there is to it by a long shot.
Wedge making is kind of technical as well which usually has to accompany the project depending on how much correction is needed. I feel the gap should be limited to no more then .010 because it tends to make the hand reach to make full contact with the ratchet teeth as well as changing the lift angle and leverage.
Some like close gaps other like them more open. Either are equally accurate if level and consistent when the light comes on. Some say tight gaps foul up less other say the opposite. I think this all depends mainly on the humidity, powder, lube , wadding and the person doing the loading rather then gap width.

 

[Stantheman86]

I'm less worried about accuracy then my gun beating itself to a slow death because the Arbor isn't bottomed out.

I still believe that Uberti tries a little harder with the big Colt repros because there's tons of famous YouTubers who shoot them and those are the ones people seem more interested in.

Probably fitting a washer is the best course of action

 

[grey8833]

Stan, could you cite your source for this information? I'm looking for "factory assembly and ordnance rebuild specifications" for the open-tops, similar to what I've found for later Colt's. I don't buy the "short arbor" theory and still wish someone would explain why wedges on originals were so carefully fitted that they were serial numbered to the gun.

I don't have the source information, but I recently fixed the short arbor on my Walker. The symptoms I had were: a Wedge that 1) came loose every third shot, 2) was beating the hell out of the barrel frame, and 3) was constantly moving into the barrel frame and was bottoming out on the barrel frame wedge screw. The short arbor was allowing the arbor to slam into the wedge (or the barrel to slam into the wedge - or both) as the barrel and frame moved under recoil, relative to each other - the restraining part on this 4.5 pound metal mass being the poor wedge). Once I had the arbor adjusted with a shim in the arbor hole (JB Weld to hold) and a "no slack" set between the barrel and the frame (arbor and barrel support) the barrel and frame were unitized (a single mass - nothing moving relative to anything else). I then had to fit the wedge to the slot with a bit of polishing on a diamond stone (thus the fitted wedge). I read on this forum that the Colt Assemblers were skilled at doing this operation and it was done by gun (serial #s all around). My recent trip to the range put 60 rounds downrange, wedge
pushed in thumb tight (no more whacking it with whatever was handy), all 60 rounds, wedge pushed back out under thumb pressure. The trick it to make the barrel and frame all one piece - that was Colts trick (patent).

 

[M. De Land]

I don't have the source information, but I recently fixed the short arbor on my Walker. The symptoms I had were: a Wedge that 1) came loose every third shot, 2) was beating the hell out of the barrel frame, and 3) was constantly moving into the barrel frame and was bottoming out on the barrel frame wedge screw. The short arbor was allowing the arbor to slam into the wedge (or the barrel to slam into the wedge - or both) as the barrel and frame moved under recoil, relative to each other - the restraining part on this 4.5 pound metal mass being the poor wedge). Once I had the arbor adjusted with a shim in the arbor hole (JB Weld to hold) and a "no slack" set between the barrel and the frame (arbor and barrel support) the barrel and frame were unitized (a single mass - nothing moving relative to anything else). I then had to fit the wedge to the slot with a bit of polishing on a diamond stone (thus the fitted wedge). I read on this forum that the Colt Assemblers were skilled at doing this operation and it was done by gun (serial #s all around). My recent trip to the range put 60 rounds downrange, wedge
pushed in thumb tight (no more whacking it with whatever was handy), all 60 rounds, wedge pushed back out under thumb pressure. The trick it to make the barrel and frame all one piece - that was Colts trick (patent).

Wedge thickness is nearly as important as it's width and if it is adequate to the barrel and arbor slots height and the arbor fits the well snugly the barrel won't be hammering itself even if the arbor is short. The arbor is supposed to be a snug slip fit into the well with or without a wedge. Jamming a tight width-ed wedge with improper thickness into a loose radial fit arbor will not stop bullet torque from moving it, that is the job of the wedge thickness fit to both barrel slots and the arbor slot and the lower bridge pins. If the slots are loose to the wedge thickness than the torque is all on the lower bridge pins. The torque load should be on both the wedge thickness fit into the slots along with the lower bridge pins.
I'm good with length fitting of the arbor but it's not a cure all by any means without a lot of other interface fitting that has much more to do with accuracy and longevity . A revolver can and will operate just as well and long with or without it, if all else is fit right.

 

[wb78963]

M. De Land,
Congratulations Sir, you have hit the nail on the head.
Thank you for such a complete and lucid exploitation.
Yr' Obt' Svt'
Bunk

 

[Lippy984]

Just out of curiosity are the wedges tapered on both sides or just one???

Good question...I assumed at first it was tapered on both sides, then looking closely and measuring with a veneer, only one side is tapered. On a new Uberti anyways

 

[M. De Land]

The wedge is only tapered on the muzzle side and should contact the arbor slot end, ideally with the same reciprocal angle in it, which usually doen't happen so the next best thing is to have a slight radius in mid slot that contacts the wedge angle. The other side of the wedge should be square and plumb with both barrel slots , one on each side of the arbor.

 

[RjSixgun]

Thanks!! I never knew that! I only briefly owned 2 brass framed 1851 Navy 44s, one was a short barrel other was standard. Being as I already owned a bunch of Remingtons I traded them off.
But now that Im older Ive been thinking about buying an 1861 Pietta just to have in the collection.

 

[M. De Land]

A short arbor causes an inconsistency of the cylinder location. That in turn means the barrel isn’t going to be in a predictable location so the best accuracy and dependable functionality is compromised.

Well, that's a great theory but I haven't found it to be true !