Trying to understand this “short arbor” on Uberti revolvers

Gino753 said:

Sorry to resurrect this, but im just getting into these guns, and my unfired 2nd Gen Colt 1851 Navy has a short arbor, and the gap between the cylinder face and the forcing cone is indeed tighter on the top of the forcing cone then it is on the bottom.I can’t fit a dollar bill in between the top of the forcing cone and the cylinder, but can just get the dollar in if the bottom

I was going to file away the top of the forcing cone to get an even gap?? So don’t do that?

Also my wedge goes in with thumb pressure just until the tip of the spring in the wedge hits the other side of the barrel wall, we’re it wants to hook under..but I need a soft tap with a rubber mallet to get the last bit of the wedge completely through? Good?

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I'm glad you haven't filed the top of your forcing cone yet, that would make your barrel fit the cylinder at an upward angle. You want that gap even and somewhere around 2 thousandths There are many fixes for the short arbor mentioned here. If the forcing cone gap is uneven, this would require fixing the arbor fit and properly machining the fit between the barrell and frame mating surface (the one with the two dowels below the loading ram). Probably something I'd take to a competent Smith with a mill

Gino753 said:

Sorry to resurrect this, but im just getting into these guns, and my unfired 2nd Gen Colt 1851 Navy has a short arbor, and the gap between the cylinder face and the forcing cone is indeed tighter on the top of the forcing cone then it is on the bottom.I can’t fit a dollar bill in between the top of the forcing cone and the cylinder, but can just get the dollar in if the bottom

I was going to file away the top of the forcing cone to get an even gap?? So don’t do that?

Also my wedge goes in with thumb pressure just until the tip of the spring in the wedge hits the other side of the barrel wall, we’re it wants to hook under..but I need a soft tap with a rubber mallet to get the last bit of the wedge completely through? Good?

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How does it shoot?

My Uberti 1851 shoots great right out of the box.

Why start fixing stuff until you know you need to.

French Colonial said:

How does it shoot?

My Uberti 1851 shoots great right out of the box.

Why start fixing stuff until you know you need to.

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Maybe he understands there's not been a 2nd Gen found to be right? Especially '51 Navy's. Typically the arbor hole breaks through at the bottom. You can get a visual of how short the arbor is . . . not to mention the originals weren't drilled through and the arbor was correct length. Some folks just understand that Italy doesn't build them by design, they are in the profit business . . . and that's totally fine.
Colts SA's (modern) are expensive yet some folks have them sent directly to a tuner . . . because if you "know" , you "know". Same with Ruger, Freedom Arms, BFR's . . .

Mike

bpalbee said:

...If the forcing cone gap is uneven, this would require fixing the arbor fit and properly machining the fit between the barrell and frame mating surface (the one with the two dowels below the loading ram). Probably something I'd take to a competent Smith with a mill

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That can actually be done a bit easier in a lathe using an arbor through the barrel. That way you know the "lug area" is perpendicular to the bore axis.

Tyler L said:

That can actually be done a bit easier in a lathe using an arbor through the barrel. That way you know the "lug area" is perpendicular to the bore axis.

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Or a file.

Mike

45D said:

Maybe he understands there's not been a 2nd Gen found to be right? Especially '51 Navy's. Typically the arbor hole breaks through at the bottom. You can get a visual of how short the arbor is . . . not to mention the originals weren't drilled through and the arbor was correct length. Some folks just understand that Italy doesn't build them by design, they are in the profit business . . . and that's totally fine.
Colts SA's (modern) are expensive yet some folks have them sent directly to a tuner . . . because if you "know" , you "know". Same with Ruger, Freedom Arms, BFR's . . .

Mike

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Also, i found that the gap between the forcing cone and cylinder ,seems to be crooked, in that the top of the forcing cone is dragging lightly against the top of the cylinder, while there is a gap between the bottom of the forcing cone and bottom of the cylinder.So the barrel gap is not even

Checking last night , it seems that the forcing cone itself was not ground flat, as the top of the forcing cone is dragging against the top of the cylinder face, while not touching on the bottom

Checking the face of the forcing cone last night with the barrel off.It seem like at the factory they laid the barrel flat and hit the foxing cone against a flat face grinder of belt sander …but moved…causing a (Slanted ) cone face

I rotated the cylinder last night,and found the gap to be the same all the way around as I rotated the cylinder.So i believe that it is simply the forcing cone

Man, I feel so far that Iver Johnson did a better job of my (F Series ) Dragoon

45D said:

Or a file.

Mike

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Very true!

Tyler L said:

That can actually be done a bit easier in a lathe using an arbor through the barrel. That way you know the "lug area" is perpendicular to the bore axis.

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Here is a 60 being lowered and leveled in my lathe between brass centers. It is by far the fastest and probably most accurate way to do the job although I have used a file and spotting fluid as well. Lite cuts are required .

Gino753 said:

Also, i found that the gap between the forcing cone and cylinder ,seems to be crooked, in that the top of the forcing cone is dragging lightly against the top of the cylinder, while there is a gap between the bottom of the forcing cone and bottom of the cylinder.So the barrel gap is not even

Checking last night , it seems that the forcing cone itself was not ground flat, as the top of the forcing cone is dragging against the top of the cylinder face, while not touching on the bottom

Checking the face of the forcing cone last night with the barrel off.It seem like at the factory they laid the barrel flat and hit the foxing cone against a flat face grinder of belt sander …but moved…causing a (Slanted ) cone face

I rotated the cylinder last night,and found the gap to be the same all the way around as I rotated the cylinder.So i believe that it is simply the forcing cone

Man, I feel so far that Iver Johnson did a better job of my (F Series ) Dragoon

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This is common with any revolver but especially so with open tops. They often will also be out of square/parallel at 3 and 9 o'clock. I check them with a feeler gauge at 3-6-9-12 o'clock and by pushing the cylinder forward and looking at the gap with a strong back light. This being out of parallel on both axis is what makes them tend to shoot off center on both axis's as well. What happens when the revolver is fired is the barrel moves forward against the rear barrel slots against the wedge and wedge against the front of the arbor slot thus unloading pressure at the arbor end. The barrel and arbor end are trying to come apart at this point. This (the forward pressure thrust at firing) is where the actual (true) barrel/cylinder gap is established as the tolerances are removed, compressed into each other and the steel elasticity is exercised.

M. De Land said:

This is common with any revolver but especially so with open tops. They often will also be out of square/parallel at 3 and 9 o'clock. I check them with a feeler gauge at 3-6-9-12 o'clock and by pushing the cylinder forward and looking at the gap with a strong back light. This being out of parallel on both axis is what makes them tend to shoot off center on both axis's as well. What happens when the revolver is fired is the barrel moves forward against the rear barrel slots against the wedge and wedge against the front of the arbor slot thus unloading pressure at the arbor end. The barrel and arbor end are trying to come apart at this point. This is where the actual (true) barrel/cylinder gap is established as the tolerances are removed, compressed into each other and the steel elasticity is exercised.

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Thank you for the reply, however it seems like although crooked..the gap between the forcing cone is still tight enough that there should not need to be anything machined off of the barrel lug? I hope..but I still have to call Mike anyway I’ve been crazy buisy today.

Im wanting to just have this gun built and fixed

M. De Land said:

What happens when the revolver is fired is the barrel moves forward against the rear barrel slots against the wedge and wedge against the front of the arbor slot thus unloading pressure at the arbor end. The barrel and arbor end are trying to come apart at this point. This is where the actual (true) barrel/cylinder gap is established as the tolerances are removed, compressed into each other and the steel elasticity is exercised.

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This IS what happens in open top revolvers with wedges that are in with "thumb pressure" , set with a feeler gauge, a smack with the heel of the hand . . . It means the wedge isn't supported and can therefore "move". If the wedge isn't between 2 fixed points, it doesn't do anything but maybe "split wood".
If the arbor isn't long enough to reach the end of the arbor hole, there's no second fixed point for a wedge to put pressure against.
The wedge imparts tension at the back against both sides of the slot in the barrel AND the front side against the slot in the arbor. Therefore, the barrel can't move forward or rearward because it is FIXED because of the wedge between the two. My revolvers wedges are factory . . . not "tool steel" . . .
The fact that I can fire +p 45acp and 45C ammo out of my revolvers with absolutely no damage is ultimate proof that "correct" design build is what allows my revolvers to survive whereas a "loose" setup ( short arbor allowing barrel assy movement) can allow anemic loads (compared) with loose powder and ball/ conical to wreck the same revolvers.
Point is, a wedge between two fixed points can impart force . . . otherwise it's just along for the ride taking up space.

Mike

I spent about an hour ..maby more.. talking to mike tonight about my pistol, as well as these types of pistols in general, and what should or is expected of them.He’s a cool guy, that cares about these things

I look forward to having this pistol rebuilt ..Fixed and upgraded, (Tuned) in the next few months

As someone who LOVES, Machines and how they work, and why they work..and the thought process and engineering that goes behind them.

I could hear the passion on the phone

Yea, he was more than generous in explaining the ROA bolt issue and how to correct it.

I had got the idea from another of his posts, but the amount I had to take off two ROA, ungh.

Nothing I have seen him present and share was wrong. We are beyond fortunate to have him here as well as him sharing what he knows with people. That is above and beyond. Generous is one word but I think it goes beyond that. Its a drive to benefit as many people as he can and if that means less work, he is good with that.

Of course he is swamped and has been for I don't know how long. At some point people like me will figure out a schedule and send him the gun as achieving his level of capability would take the amount of time he has put into it to get where he is.

But you take out the time he talks to people? Hard pressed to express the appreciation for that.

I have been able to get my 47 Walker Workable, but all the refined upgrades, that is what 45D does.

My 1978 London model Uberti 1851 doesn't have any of the arbor issues. When did this become a problem, or am I one of the lucky ones?

fistmil said:

My 1978 London model Uberti 1851 doesn't have any of the arbor issues. When did this become a problem, or am I one of the lucky ones?

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Interesting, what makes you say that?

Mike

45D said:

Interesting, what makes you say that?

Mike

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Well everything seems to line up and fit together fine. I've fired close to 2000 rounds through it and the cylinder forcing cone gap is still square, wedge has no play in it and barrel doesn't move. I use a wooden mallet to remove and reinstall wedge and it seems to fit together as good as ever. I'm no marksman buy a long shot, but it's capable of 3" to 4" groups off of a rest at 25 yards. I shoot 18 grains of 3f black powder and a .380 ball. The only thing I have had to replace was the cylinder stop bolt.

fistmil said:

Well everything seems to line up and fit together fine. I've fired close to 2000 rounds through it and the cylinder forcing cone gap is still square, wedge has no play in it and barrel doesn't move. I use a wooden mallet to remove and reinstall wedge and it seems to fit together as good as ever. I'm no marksman buy a long shot, but it's capable of 3" to 4" groups off of a rest at 25 yards. I shoot 18 grains of 3f black powder and a .380 ball. The only thing I have had to replace was the cylinder stop bolt.

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The arbor is likely not making end contact but most of them still in use are not end fit , many have been that way for decades and still keep right on working .
They can be made to fit more precisely being tuned up with mods through out but all these improvements are not essential to their function for the average shooter.
Virtually all Uberti's and Pietta's will function left as received if lubed and cleaned properly.

fistmil said:

My 1978 London model Uberti 1851 doesn't have any of the arbor issues. When did this become a problem, or am I one of the lucky ones?

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My 1851 as well, no one wants to believe it.

Average! I'll have you know I've been known as an under achiever all my life. If all these revolvers have the short arbor, and it seems worse with some than others. Do the newer revolvers have a tendency to be worse?

fistmil said:

If all these revolvers have the short arbor, and it seems worse with some than others. Do the newer revolvers have a tendency to be worse?

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They're all short (Uberti's) and have been since some time in the '60's. As far as some being worse than others, that will depend on how it's used. The Navy has more material than the Army so it handles its lighter powder charge better. Therefore, it's not going to exhibit the problems associated with heavy loads used in Army's and of course the horse pistols. Your fully loaded Navy with 18gr charges would almost fill 2 chambers in a Dragoon/Walker.
The problems for a Navy with a short arbor are more about "same assembly" each time it's reassembled. I'm positive though that since there is space at the end of the arbor, it would be better and probably more accurate.
With the "big guns", the loads are much more punishing and cause structural problems. So, bottom line, if it doesn't bother you that your Colt "copy" isn't quite right in the most important area, don't worry about it.

Mike