Cimarron Open Top issues--Update

[OD#3]

I took delivery of this today, and it looks like I'll have a lot of work to do.  I would have preferred something in .44, but these are hard to find; everyone seems to want a .45.  So this one is in .45 Colt.  I'm well aware of the history of weaknesses that develop with these in such a fat cartridge, but most of the reading I've done lately claim that Uberti addressed these issues by beefing things up a bit.  If this is Uberti's "beefing up" result, I can see why so many folks still recommend to stay away from these in this caliber.  Cylinder diameter is smaller than SAA, and the outside chamber wall thickness is a good deal thinner as well.



SAA...


Open Top...


SAA on left, Open Top on right...


Open Top at about .042


SAA is thicker at about .062


I measured the forcing cone over the arbor cutout at about .042 as well...


I've seen other posts where this was measured at .039, so perhaps Uberti has, indeed, beefed it up just a tad.  I don't know what others' measurements of the outside chamber wall thickness was.  It appeared to me that it wouldn't detract from the overall lines much if Uberti just beefed up the cylinder to SAA diameter with some accompanying enlargement of the barrel assembly as well.  But perhaps they've made some metallurgical iimprovements.  Time will tell.

I'd like just once to purchase an Italian clone that was ready to go out of the box.  Everything I buy needs work.  As expected, the arbor hole is much too deep...


And the action is rough as a cob.  Burrs abound.  This one was protruding out of the hand slot.  It rubs against the hand something fierce.  I don't know how they managed to time this thing (though I'm going to have to address a few small timing issues as it is).


But the first thing I'm going to have to address is the endshake.  This thing is going to batter itself to death like it is.  I've probably got .020 or better endshake on this thing right now.  I could pound the wedge in deeper, but that would just torque the top part of the barrel in at an angle and probably deform the wedge slot as well.  How do most of you do it?  I"m thinking of pulling the frame pins and dressing down the front of the frame.  The gas ring is set at a good depth for barrel cylinder gap; I just need to get the barrel assembly to sit deeper against the frame to snug that cylinder up.  Then I have to hope that the headspace won't be too tight as a result.

Uberti makes a pretty Open Top, but I'm not too impressed with how they put it together.
 

[OD#3]

End Shake

[Fox Creek Kid]

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[Crow Choker]

OD, if it were mine and I had so many reservations about it, I'd send it back and request another if your not happy with the quality. If you have this much disappointment now, you may never be happy with it, I know I wouldn't. Maybe Cimarron can get a 44 for you. All of Cimarron's claims to superior quality over any other Uberti import is not true, many have found that out. Read my post on the American Plainsman Society on this forum originally started by 'Rabbit', titled "Quality of Reproductions" on the problems I had with my first Open Top I purchased from Cimarron. From what I've read, most of the 45 Colt caliber problems of the past have been rectified as far as cracking in the forcing cone area, but that doesn't erase the rest of your concerns.
Yers, Crow Choker 

[OD#3]

That is tempting Crow, but I think I'd be playing the lottery.  I have NEVER received an Italian clone (revolver) that was ready to go as received.  The Pietta Thunderball was the worst ever, but this one certainly has its issues.  The timing and rough action I can handle.  When I get finished with the action, it will be smooth and perfectly timed; I've had a lot of experience with that of late, and I'm confident in my abilities there.  I expect to have to tune any Italian single action, and I think I'd rather just fix this one rather than go through the hassle of a return only to get some other problem with the replacement.  The cylinder gap when the gas ring snugs against the barrel assembly is excellent, and the headspace is good when the back of the cylinder is snugged up against the frame.  So I'm really leaning towards dressing down the front of the frame, so that the barrel assembly is moved to the rear slightly.  My only concern is the fit of the wedge after.  I'll do some careful considering on that.  Regardless, dressing down the front of the frame to correct open top endshake is something I have no experience with and can find little information about.  Incidentally, anyone know the best way to remove the locating pins on the front of the frame?

[Coffinmaker]

The locating pins at the front of the frame are press fit.  They (Uberti) tap them in with a small hammer.  Some are knurled to enhance retention.  Removal is usually fairly easy with a Vice Grip.  Insure you have new replacements handy.
Good Luck with your Open Top

Coffinmaker

[45 Dragoon]

Check the clearance with cases in, it may just need the arbor length addressed. Do your tuning with empty cases in. Since there is a bushing (gas ring) I'd prob. Start with .003 gap.  Conversions (I know the '72 isn't one) dont have a bushing and can get away with a tight .002 clearance or end shake.

 If you need to remove material at the lug/frame (after correcting the arbor length) remove the pins (Uberti -good luck) and use lapping compound. The frame will lap into the barrel assy. It's not too bad a job but better than trying to file a perfect fit. What you end up with is a nice steped (however small it may be) fit with more surface than the orig. straight cut.

Mike
www.goonsgunworks.com

[Coffinmaker]

Before your do much of anything else, you need to address the Arbor/Barrel fit.  Nothing else will fall into place until the arbor fit is correct and you have fit the wedge.

Coffinmaker

[OD#3]

Guys, I really appreciate all of your help on this.  I hadn't considered lapping, and the suggestion did not appeal to me at first.  But I think that I may go that way afterall.  My only concern there is the repeated twisting of the barrel assembly on the arbor during the lapping.  I'll lube it well, but I hope it doesn't loosen on me; it is a very snug fit right now. 

Coffinmaker, you've been a great help on this forum, and I would usually follow your advice without further question.  But it strikes me as impossible to address the arbor length correctly until I've set the whole barrel assembly back as far as it needs to.  Only then will I be able to assess exactly how much to lengthen the arbor and address the wedge fit.  These measurements would change if I tried to do that first, don't you think?

[45 Dragoon]

Coffinmaker is right. Like I said, do the lapping after you correct the arbor length. Keeping the barrel on the correct plane as you lap is why. 1st, The arbor is defined and the hole will be brought up to meet the arbor. 2nd, recover the b/c gap. Depending on how severe the situation is, you may dress the arbor as you move everything back (lapping). Stop when you reach your spec. (Empties in!)  Finally, bed the end of the arbor (will erase any "wear" caused during lapping). You may find it easier to retain use of your orig. wedge by installing a set-screw in the end of the arbor (grind the set end smooth ( it can also be called "an adjustable bearing")).

Mike
www.goonsgunworks.com

[Coffinmaker]

OK.  Lets just look at the problem as it actually is.  The arbor isn't the problem.  The hole in the barrel is the problem.  It's too deep.  That slop has to be taken up first.  There are three ways to do it.  You can line bore a hole in the end of the arbor and install a Dillon locator pin in the end of the arbor then dress it to correct the barrel fit to the end of the frame.  You can line bore the end of the arbor, thread the bore and put a screw in the hole.  Dress the screw to take of the extra space so the barrel seats correctly and aligns with end of the frame.
Or, go cheap seats and quick and drop a 5mm split washer down the hole and shove the arbor in.  Install the wedge.  So long as the wedge snugs up well with thumb pressure with the retaining screw turned into it's slot, your gold.  Then you can proceed to address the end shake. 
Judging by the gap between the barrel and the end of the gas ring on the cylinder, your chasing your own tail with the gun you have in hand.  It needs to go back.  The assembly folks at Uberti screwed the gun up pretty badly.  With an Open Top, the head space need to be measured with cases in the cylinder.  Optimal head space between the case head and recoil shield is optimal between .004 and .006.  I like .005 when I can get it.  At about .005 head space, end shake should be around .003.  There needs to be some room to move around.  After you have achieved that, you can address barrel/cylinder gap.  Should be .005 - .007.  Only after you have corrected the above things can you do a meaningful action job. 
I'm not holding your gun in my hand, taking my own measurements so I can't determine from afar just how much everything is screwed up.  But.  If you choose to set that barrel back first, you may just screw yourself into the floor.  I should strongly suggest you spend a nickel for a stainless 5mm split washer, drop it into the hole and see what you've got.  You may just find the dimensions are screwed enough the only answer is to ask for another gun.
Uberti built guns are "kits."  Pre-assembeled kits.  I've pontificated long and loud what I think of Open Tops and conversions chambered in .45 Colt.  The cylinder can't be expanded any more without an enlargement of all the other major components.  A look at a Uberti Type II Richards conversion will show just how bad that screws things up.
If you take the time with the split washer, you may find you don't have enough gas ring on the cylinder to set end shake.  Then you get into having to cut away the gas ring, rebate the cylinder for a new gas ring you have to make yourself.  Or your machinist.  Find out what you have first.  Personally, I'd send it back and start over.

Coffinmaker

[OD#3]

My premature attempt to remove the pins has probably ruined any hope of return; I chewed one of them up in the attempt before penning my thoughts here on curing this open top's ills. 

Please understand; I'm not being intentionally obtuse.  I value your expertise, Dragoon and Coffinmaker, and I'm very grateful for it!  But I'm still failing to grasp the reason for the arbor fittment first, albeit conceding that my prior experience has been entirely with SAA's and double-action revolvers of both S&W and Colt.  This is the first open top I've ever messed with.

Headspace with empties and the cylinder snugged against the recoil shield is good.  And barrel-cylinder gap when the gas ring is snugged against the barrel assembly is good.  But the barrel assembly snugs up against the frame with the gas cylinder well shy of touching the barrel assembly.  So the fix seems (admittedly to someone with experience in revolvers other than open tops) to be just moving the whole barrel assembly to the rear until the gas ring reaches the barrel assembly.  The only unknown there seems to be the eventual fit of the barrel wedge; it might end up too loose after I move the barrel assembly back (but I don't know yet--it was pounded in pretty tightly just to allow enough clearance for the lock screw to turn before).  The arbor hole depth is too deep, but that looks like something that can be addressed once the barrel assembly is moved back as far as it needs to be for correct headspace and endshake. 

I have two open top experts telling me that I need to address the arbor hole first, one of them suggesting that this may be hopeless.  I can't send this back now, so I'm going to have to make the attempt.  It is going to be an education no matter which way I go (I've been spending 400+ bucks a pop lately buying Italian clones that educate me on curing their ills).   I'm certainly willing to defer to your expertise; I've read enough of Coffinmaker's threads to know that he knows what he's talking about, and Dragoon's shop has an excellent reputation.

So I beg both of your indulgences and patience.  Can you explain again why the arbor hole depth is the first thing to address?

Thanks so much for lending your experience and expertise here.

 

[45 Dragoon]

Thanks OD#3,
  Establishing a correct alignment is needed to have a starting point. You need something to measure from so you're not throwing darts in the dark. I use s.s. flat washers set with an epoxy to correct the hole depth (a shim cut from the appropriate sized feeler gauge can be used to fine tune later if needed). For me, the arbor is an excellent guide for any needed lapping. My specs. call for a .002 barrel /cyl. clearance, so fixing the arbor length is just the first step. Then, if reaching the .002 clearance has the bbl. lug meeting the frame too early, then lapping is needed. Understand that when the wedge is installed, a certain amount of torque will be introduced so you cant "eyeball" the gap without setting the wedge. The bbl. and cyl. gap should be equal from top to bottom ( no pie shaped gaps!).
   If lapping is needed, you will also be dressing the arbor end as you go. (See, without a corrected arbor, you dont have a good guid for this step.) The frame is harder than the bbl. so it will eat into the bbl. lug and form a step. I think that's a nice by product of lapping because it produces a stronger joint than just the butt joint that was there. As you mentioned, the pins in an Uberti usually break off, Piettas will come out clean. If you can do this procedure, you wont have trouble drilling out the old and making new.
  When/as the lapping is done you will run out of "wedge"  at some point. My spec. calls for an adjustable arbor bearing anyway so drilling and tapping the end of the arbor is the norm for me. Can't remember the dia. of the arbor in the '72 but probably a 1/4" (used in all the big guns Walker, Dragoons etc.) or a 6mm (Armys/Navys) set screw will allow you to keep using your wedge. In my process, the set screw is ground flat so the bearing wont cut into the wedge. When you're done, you now have the foundation for precise tuning.

Oh yes, I deal with non-gas ring/bushing OTs and they are self cleaning as you cycle the action. This keeps any build up off the cyl. face so you can maintain a really tight clearance. With a true dedicated bbl./cyl. gap, .003 is as small as I would go. All mine are .003- .005 .

 Ultimately, it's the length of the cylinder in your revolver that determines how much and to what degree you go to for the numbers your looking for. Go slow, it takes time, the results are amazing (done correctlly). Stop when you "think" your done (you can adjust it later).
  I'm good with a file, can give a polished look with a file, but believe me, lapping is easier and produces a better fit.
  
  Good luck,
Mike
www.goonsgunworks.com


Note: the size of the set screw for Armys and Navys is a 6mm not a 10mm. Apparently, I hadn't had my second cup of coffee this morning!

[Fox Creek Kid]

...Can you explain again why the arbor hole depth is the first thing to address?...

Because since there are two halves to the gun you need a solid reference point, a mechanical 'zero' if you will. If you don't then you will be 'chasing' a proper juncture. Properly fitting the arbor gives you just that.  

[OD#3]

Well, I followed the advice here about the arbor, and I was a bit embarrassed that I hadn't immediately seen that as the way to begin in the first place.  I used the method most recommended, in that I drilled a hole in the face of the arbor that would accept a large-headed pin that I could dress down to the proper length.  One thing I hadn't noticed before and which, if it was even mentioned on other DIY's, is something I don't remember ever reading before, is that the bottom of the arbor hole is not flat.  Had I to do it over again, I think I'd have tried to match that contour better with the headed pin that I machined.  As it stands now, my pin head  is slightly curved but not completely.  I get more contact than if I'd machined my pin head perfectly flat on the face, but I think it could be better.

I used a drill press as a lathe and machined a small bolt down to about the size of a Dillon #3 locator pin.  I wanted to use steel instead of brass, so I went with the bolt.  There was a lot of fit and try, and more fit and try at the end, but I have achieved zero endshake.  Lapping the barrel assembly against the frame took a lot longer than I'd expected, but I have that achieved now, and I'm happy with the fit.  HOWEVER, I didn't use your adjustable drilled and tapped arbor bearing method Dragoon, so as I feared, it looks like I"m going to have to do some work to the wedge.  It bottoms out without really torquing the barrel assembly very tightly against the frame.  It looks like I have enough room left to work with the wedge slot in the arbor, but I'm going to have to remove some material from the front of the slot on the barrel assembly and tig weld some material onto the back of the wedge and dress that down, if I want a good fit.  In essence, I'm going to have to make my wedge just a little wider.

I have a lot more to do, and this won't really have been worth it in the end except for increasing my hands-on knowledge of how to work on these things.  I don't have any in-progress pics, but I'll post some pics later detailing some of the work if any one is interested.  

[Thumb Buster]

I believe it is Coffinmaker who continually calls these reproductions 'kits'.  Got so use to it I now enjoy fiddlin' with 'em and learn something new every time.  ...Preassembled kits...    

[45 Dragoon]

Nice job OD#3,
 Now you know why I bring the bottom of the hole up instead of lengthening the arbor. Stacked steel shims give you the flat bottom you want for arbor contact. The adjustable front wedge bearing (BIG set screw with smooth end) allows the use of the original wedge. Of course, your fix will be fine or you could still use the threaded end for a screw and shim the hole (and use the wedge you have).

Mike
www.goonsgunworks.com

[OD#3]

I considered threading the arbor hole for a set screw, but I'm worried about how much contact are I'll have.  Uberti machines these wedges now with a curved forward edge.  It looks like even a large flat-bottomed screw would concentrate too much force against a relatively small area of the wedge.  But that is only conjecture.  You're the one with the experience here.  Any issues?

[45 Dragoon]

If you look at the forward bearing surface on a Pietta, you will see that the way they cut the wedge keyway leaves a smaller surface. The set screws I use are basicly the same size as that surface. The main thing to understand is that the contact with the bottom of the hole is where the transefer of energy from one assy. to the other happens, not the wedge. The wedge WILL get beaten up when the arbor is too short (for the reason above).

 Mike
www.goonsgunworks.com

[45 Dragoon]

My method works great for me and my customers. Maybe you can figure out a better fix . . . . .

Good luck with your O.T.

Done.

Mike
www.goonsgunworks.com