Cimarron 7th Cavalry cylinder rotation hang-up

[OD#3]

If you read my last post on my recent acquisition of this revolver, I gave the impression that this was a very fine revolver that benefited just a little from some minor stoning and bolt leg work but was otherwise fantastic.  Well, I spent most of the afternoon correcting a little problem, and I'm curious how many others may have encountered this. 

When I was testing cylinder rotation with a loaded cylinder, I found that the cylinder felt like it was binding on something whenever the muzzle was pointed at the sky.  Further investigation revealed that the rims of the cartridge were catching on some rough machining on the breech side of the recoil shield.  Here is the offending areas.



There was a slight difference in height between the loading gate shank area and the recoil shield.  This height difference was only very slight, but some of the cartridge rims were catching momentarily on this sharp edge.  But the worst area was the ledge created by the rough machining on the left side of the shield.  Now as I imagine the manufacturing process, the headspace area at the top is critical.  So I guess that Uberti finishes this area carefully but then has to blend the loading gate shank into the rest of the recoil sheild, and this often causes the lower part of the shield to be machined deeper than the headspace area at the top of the shield. So somewhere along the way, these two areas have to meet, and the transition should be as smooth as possible.  I noticed the same "step" in the recoil shield of my Colt, but the transition is much smoother, and rounds don't catch on it.




So I tore her back down again and got the stones out.  I first attempted to attack the following area shown in pink with small stones and a cylindrical stone.  This proved very difficult to get a smooth transition, and I was noticing that the area shown in yellow was actually a shallow depression caused by some rough machining.



Eventually, I switched to larger stones and increased the area of my blend.  I was careful to stay away from the actual area where a cartridge would be sitting under the hammer, so as not to increase the headspace any.  But the total area stoned became quite large.  Eventually, I'd eliminated the machine marks and created a smooth transitional surface from the deeper area at the bottom to the shallower area at the top.







Of course, this now left a large bare patch of steel that I had to hit with some cold blue.  I dabbed it on with a cotton swab, attempting to mottle the color a little bit.  It turned out better than I expected.



I also beveled these areas shown, though this is only a "before" photo; I forgot to take an "after" one.



Now I can put it on half-cock, point the muzzle at the sky, and rotate a loaded cylinder without any hint of a hitch in rotation.  However, it was suggested by someone else that I had gotten carried away with the stoning and had eliminated an important part of the recoil shield--that "step" that the other person claims is present on all single actions and is somehow important to the design.  He said that mine was too sharp from the factory but I got the impression that he believed its presence was necessary. 

My thinking is that since I did not touch any area covered by the rim of a cartridge that was actually being fired, that I did no harm.  But I'd be interested in your opinions.  I'd also be very interested in pics of other's recoil shields in this area and/or anyone else's experiences with cartridge rims catching on these areas. 

I'm hoping to get to the range next week, and I'll post a range report then.

[Major 2]

You take some very fine photos ....

since you asked here is a photo of the area on my new to me Uberti Model P #MP4502
Note: the FP bushing , I have not held the gun as yet as it is in route ..

I see the step you illustrate, and it is present on my USPFA  USFA/Uberti nickle Store keeps as well ( no drag )

[Kent Shootwell]

Here's how a USFA Rodeo, a ASM Heritage and a Ruger old Vaquero looks. I'm sure yours will be fine. The Ruger has a step like yours.

[OD#3]

Guys, I can't thank you enough for sending some pics (very good ones at that).  Major2, that isn't fair that yours has a firing pin bushing.  Did the previous owner install that, or do all the stainless ones come with it?

Kent, I hope you didn't detail strip that USFA just to take a photo for me.  But if you did, I thank you very much and thanks also for including the Heritage and Ruger as well.  You both have confirmed the existence of, and probably the necessity for there to be more wiggle room built in to the system for the cartridges not directly under the hammer.  I guess the design allows more dirt tolerance that way, and my problem was just that Uberti didn't bevel that step enough.   I suspect now that I probably didn't need to smooth mine as much as I did, but I'm confident now that I didn't hurt anything.

Thanks again,

Eric

[Major 2]

This is the first SS model I've handled , and it came from a private owner not a dealer.

The date code is [CM] or 2014 and is new in box or at least ANIB ... the correct box & papers are included
The description stated it was a custom, and built sheet/ invoice ...
stated work carried out... Premium Action Job & springs , Forcing cone cut to 11° and polish, FP Bushing work & relieve hammer & polish,
detail polish ...
It has also been fitted with Genuine Colt grip frame Trigger Guard & ejector rod in polished blue for contrast .

The work is FIRST RATE and a sweet running piece    I plan to shoot it tomorrow.

[Coffinmaker]

The area where the cartridge head spaces needs to be "left alone" although you may find yourself stoning away burrs around the firing pin hole.
The area of the recoil shield to the "right" as the cylinder rotates opens up a few thousands to permit smooth operation even with a minor primer back-out (they all back-out), and to assist operation with "slightly" high primers, when rotating the cartridge into battery, yet maintaining correct head space.
Long way of getting to "the step is suppose to be there."  The sharp "ledge" is not.  It is suppose to be a nice smooth transition.  Cartridge rims are also provided with a tiny bevel to assist the smooth rotation of the cartridge onto the "firing platform."

Coffinmaker