1872 Open Top Problem

[Capt. Augustus]

One of my open tops is giving me problems.  I looked over the tuning of the Uberti Open Top and I just don't know.

I noticed that the rear portion of the cylinder was being marked, that is between the bolt holes and the rear edge, but otherwise it worked okay.  Well, in the last match the gun started hanging up and the cylinder would not turn, or would stick and then over rotate. So I decided to take it apart and have a looksee.  Without the barrel installed the cylinder rotates as it should with no hangs.  As I slide the barrel on the frame and the alignment pins seat the jams come back.  I read the portion about the fitting of the arbor and checked the alignment of the barrel pins to the arbor and it is real close to being perfect, but as the barrel seats into the frame, it appears to be putting pressure on the arbor causing the rear of the cylinder to drag.  I made a gauge of newsprint and it will not clear the frame to cylinder behind the bolt holes with the barrel installed.

Any help would be appreciated.

[Adirondack Jack]

Just a guess, but try a thin shim of some sort (maybe a layer of tape or two) on the nose of the arbor.  I'm told they are supposed to bottom in the arbor bore in the barrel.  If your arbor is too short, which will cause a camming action when the wedge is installed.  A very thin washer or some such (snippet of soda can perhaps) in the bottom of the bore will shim it.

[Pettifogger]

On many of these guns the clearance between the cylinder and frame is almost zero.  Any misalignment of the arbor and the cylinder drags.  Your experience indicates this problem.  When the barrel is off the arbor is moving slightly upward.  When you put on the barrel it is pulling the arbor down and the clearance goes away.  Check the frame to make sure there is no dirt, debris or burrs near where the cylinder is dragging.  I had one that was giving me fits.  Finally noticed that the rectangular hole where the bolt comes through the frame is apparently punched and the punch must have been misaligned as there was a ridge on the backside of the hole.  After cleaning up the area it worked fine.  Without seeing the gun its hard to tell whether the arbor is misaligned, bent, or there is some other problem.  Working with these things involves a lot of detective work to find problems on some of them.  The problem is particularly bad on the models with rebated cylinders.  On some the alignment pins are actually machined a little and have a flat facing up.  Make sure the pins haven't moved if they have these flats.

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[Capt. Augustus]

Pettifogger,  I checked the frame and removed a burr near the bolt, but it didn't help.  I looked at the pins and they are round I'm wondering if I should try Uberti's trick and take some off the tops of the pins, they are cheap enough to replace

[Capt. Augustus]

Thinking about it maybe the bottom of the pins since putting hand pressure down on the arbor seems to duplicate the problem.

[Abilene]

Howdy Capt.
I assume this is a new gun, and not one that was working fine and then started having the problem?  Anyways, taking a little off the bottom of the locator pins sounds like it might do it.  But one other thing you might try is to remove the cylinder, then degrease the part of the frame in the area where the rubbing is likely happening, then use a magic marker or sharpie to "paint" that area of the frame.  Then install the cylinder and push the barrel on enough to get it to drag for just a bit, then remove cylinder and look for where the marker ink is rubbed off.  Then you might find out exactly where it is dragging and decide if you want to do a little sanding there.  If it is right on a side edge you would need to be real careful. 

[Capt. Augustus]

Thanks to all of you.  The filing of the bottom of the pins got it turning again.  I'll take her to the range and see how she does. 

I blackened the frame and nothing showed, who knows, I sure don't.  It's not a new gun, but has spent most of the past 3 years in the safe taking it easy.  Like I said the wear on the cylinder shiwed up then, but she kept working, waiting for the match no doubt.
This is almost as bad as when the loading gate on my Ruger .32 was interfering with cylinder rotation.

[Capt. Augustus]

Well, took it to the range and put 50 rounds through it.  I didn't get any jams, but I can see that some rubbing is still taking place, so I'll take a harder look at the frame and bring it down a little.  The fun of it all.