Perhaps the current open top tuning wisdom has some things backwards?

[Im2bent]

Hoping that headline garners some attention. So here goes. Currently conventional wisdom is to address arbor fit first. The problem is if you have excessive endshake correcting the arbor fit will just make your endshake permanent. Had I known this beforehand I would have approached things differently. I believe you should remove your wedge to release any undue pressure from a short arbor and firstly check for excessive endshake because the only way I can think of to diminish endshake is to remove material from the barrel/frame interface which will change the arbor/barrel fit. On my pistol I went full speed ahead and followed the guide and "fixed" my arbor fit, now I have a lot of endshake to deal with which means the work I did fitting the arbor goes out the window if I remove material from the frame or barrel to reduce the endshake. Thoughts?

[Coffinmaker]

HAVE YOU SHOT IT YET??

[Im2bent]

Well at this point its about clarification. Everywhere I have found posts on this site regarding this issue everyone (including you) say that this level of endshake is unacceptable. In the post by Russ123 you said "It's simple actually.  Barrel to cylinder gap is optimal at .005/.006 and .018 is unacceptable" and "Your gun doesn't meet any of that criteria.  SEND IT BACK.  In fact, SEND IT BACK for REPLACEMENT" you did not tell him to just shoot it.  And Mike of 45Dragoon says he sets it at around .002 thousands. So which is it? Just shoot it or will this level of endshake  lead to long term damage,excessive blowby of gases,spitting of lead shavings out the sides,etc? Not trying to cause a ruckus just trying to figure things out. As always the help of those in the know is truly appreciated, it's just that conflicting advice leads to confusion. I am starting to wonder if the problem isn't that Uberti arbors are short but that the frames are long?

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[45 Dragoon]

Ok

    Im2bent, you posted that this is a new Dragoon. I have all confidence in Uberti that the frame is just fine. Starting with the frame/barrel lug joint (interface as you call it), that is the  "fulcrum" in this situation. It is correct.

   The arbor length is what defines the barrel assembly's position. Knowing that ,  .015" bbl/cyl clearance is definitely excessive.  Understand that since the clearance we want to "adjust" is  above the arbor (remember the fulcrum ( barrel  lug/frame) is the "constant"  at this point)  it won't  be a 1:1 closure as you remove material from the button you installed on the arbor. Furthermore, the clearances between the arbor and the arbor hole won't be totally eliminated just with the wedge installed. The wedge should impart tension to the  union of the barrel assy / frame assy which will give you a true reading of the bbl / cyl clearance. So, remove material from the button ,  install the bbl , drive the wedge in and measure the clearance. Repeat  until you reach your clearance spec.  When your spec has been met, there may be a slight pie shape to the bbl /cyl opening. You can clean it up by carefully filing  (probable slight adjustment of the clearance to regain any spec. loss).  The barrel should end up with correct alignment (more or less) but the main thing is it will be the same each time you reassemble the revolver.
   Ultimately, the solid union of the two assemblies will react as a single unit and harmonics won't be a detriment to the revolver (which is usually the reason for early demise).

Mike

  If you've dressed your wedge very much, you may need a new one as the wedge slot will be opening as you remove material from the button.

[Im2bent]

Thank you for your reply 45 Dragoon. I followed your advice and removed button material to close the gap. i did indeed have to tig up my wedge. I now have .006" clearance. Of course I have to give the wedge a rap to basically pre-load the barrel but that's no biggie and I think I read somewhere that that is/was the recommended procedure from Colt anyhoo? Thank you to everyone who helped me on my learning experience and if I ruffled your feathers Coffinmaker my apologies that was not my intent. I threw on a set of slixshot nipples and she is ready for battle.
Due to my experience with this Uberti and Coffinmakers recommendation to go Pietta I now have a brand new Pietta 1851 Navy steel frame in .36 to go through. It will be interesting to see what the differences are. Right off the bat I did not have to pry off the barrel so thats a plus right there .

[RUSS123]

Well at this point its about clarification. Everywhere I have found posts on this site regarding this issue everyone (including you) say that this level of endshake is unacceptable. In the post by Russ123 you said "It's simple actually.  Barrel to cylinder gap is optimal at .005/.006 and .018 is unacceptable" and "Your gun doesn't meet any of that criteria.  SEND IT BACK.  In fact, SEND IT BACK for REPLACEMENT" you did not tell him to just shoot it.  And Mike of 45Dragoon says he sets it at around .002 thousands. So which is it? Just shoot it or will this level of endshake  lead to long term damage,excessive blowby of gases,spitting of lead shavings out the sides,etc? Not trying to cause a ruckus just trying to figure things out. As always the help of those in the know is truly appreciated, it's just that conflicting advice leads to confusion. I am starting to wonder if the problem isn't that Uberti arbors are short but that the frames are long?

Or both? Just theorizing here so don't get too excited. (brain farting if you like)

Frame too long! Sure, why wouldn't you think that. The problem is: There are no specifications to go by like you would find in a 1911 or a Colt SAA or a Ruger SA Shop Manual written by Jerry Kuhnhausen. I happen to have 3 of his manuals.

Pettifogger's instructions leads you to think that if the barrel lower body meets on the same plane as the forward end of the frame when the Arbor comes to rest in its hole,..... the Arbor is at its optimum correct length. If short, the barrel's lower body would overlap that plane to show just how short it is. Nothing further than that is addressed. If short, the Arbor is simply lengthened by various means.

OK, so, let's assume by some hidden specification that the frame length is correct as well as the arbor, either by luck or by correction.  Where does that leave us to a cause if the clearance/gap is still unreasonably too wide?

Could the cylinder be too short by a few thousandths?
Could the forcing cone be too short by a few thousandths?
Could it be over machining of the breach block surface the cylinder ratchet rotates in?

Could it be the stacked tolerances of all 3? Yes, of course. Did I miss anything?

Without specifications there is no way someone could draw a conclusion on which part or parts of the assembly is in error. So what do we do? Well, it appears we have no choice but to improvise with what we know and make it how it should be (gun meeting criteria), because... as it has been written before on this forum, these are really suber looking "KIT" guns.

Uberti's owner's manual on mine states that: If the cylinder binds after reinstalling the barrel and wedge... to back out the wedge a little to free it up. Can you believe that? I'm in belief that Uberti purposely machines their Arbors too short.

SEND IT BACK to Cimarron?  Good god why? What would I say to them? My friends on the CSA forum say the Arbor is too short and I think the gap is too wide? Cimarron would probably send it back to me stating it's within specification and the action functions just as it should, no fix necessary...

The truth is: The action to my 1872 is, in fact, very smooth, locks up fine, timing good, etc. no problem there. Forget warranty... of to Mike it went.

[greyhawk]

Hoping that headline garners some attention. So here goes. Currently conventional wisdom is to address arbor fit first. The problem is if you have excessive endshake correcting the arbor fit will just make your endshake permanent. Had I known this beforehand I would have approached things differently. I believe you should remove your wedge to release any undue pressure from a short arbor and firstly check for excessive endshake because the only way I can think of to diminish endshake is to remove material from the barrel/frame interface which will change the arbor/barrel fit. On my pistol I went full speed ahead and followed the guide and "fixed" my arbor fit, now I have a lot of endshake to deal with which means the work I did fitting the arbor goes out the window if I remove material from the frame or barrel to reduce the endshake. Thoughts?

I am bent also - I also am not up to speed with the "lingo" being an aussie and all (Coffinmaker thinks thats because we all standing on our heads)

It is (I think) possible an old gun might benefit from removal of some metal from the barrel / frame joint, (Mikes fulcrum - lets get back to that in a minute or two) -
If Uberti and Pietta are on their game at all this should not be necessary on a new gun but we shouldnt need to adjust arbour length either??

I did this operation to an old walker belonging my son - been shot a lot, and always full charges, had maybe 20 thou cylinder gap/endshake and when we flogged the wedge in far enough to get an appropriate measurement then the resulting vertical wedge shape gap was very disconcerting (practicing long words here!)

So I went ahead and took (carefully) 10 thou off that surface - ooooopsy - did this in the lathe - cant remember exactly how I held it - thought I had a good setup but forgot the tendency of a stop/go cut like that to remove a tad more metal from one edge of the cut than 'tother

Had left meself some wiggle room so got that sorted straight with total removed of 12thou

ok the fulcrum ---the pins were worn and loose so I decided to drill those oversize and make em neat fit again - NO! these guys need a tiny bit of room to move - that gun was just a tad too stiff - it has worn in ok but I got a bit carried away with that. Dont forget that this fulcrum business is also gonna affect your point of impact on target

Of course I adjusted the arbour fit as per instructions from Pettifogger, Coffinmaker, Mike

In the end this old gun is better than it ever was new - 6 thou cylinder gap, chambers reamed out (it measured .462 grooves with chambers at .454) - It will shoot a nice group with a full charge now - never would before. I expect if he keeps shooting 65 grain loads it will need more work at some point but  an awesome fun gun in the meantime.

       

[RUSS123]

The fulcrum business:

I believe the only thing Mikes was trying to point out about the fulcrum was just a bit a caution about removing material off of the added Arbor button. Why? Because, from the fulcrum, the Arbor is at a shorter "radius" than the barrel which means: Material removed from the button will have a greater effect at the barrel due to its greater radius. For example: Removing .004" off the arbor button will show up as a .006" reduction in clearance at the barrel, assuming a 1 to 1.5 ratio difference in radius but that may be somewhat exaggerated for the sake of simplicity to the example. Mike is just giving caution to this. Take it down slow and recheck often.

The Point of aim question? That depends on you sights but let's see what happens to the barrel...

Lets calculate the amount of rise to a 7.5" barrel with a clearance change of .010". This will be based on a rough estimated radius of 1.5". First, I want to know what 1 degree of rotation equates to in thousandths of an inch for a 1.5" radius.

Radius = 1.5" or 3" Diameter. Convert to thousandths or 3000.
C=Circumference of a Circle
C=Pie X D
C=3.14 x 3000 thousandths
C=9420 or the circumference in thousandths for a 1.5" radius.
9420 divided by 360 = .026"

What I figured is: 1 degree of rotation equates to .026" for a radius of 1.5 inches. So, a gap change of .010", equates to only .38 degrees (or 22 minutes) in rotation.

So the question: How much of a rise to a 7.5" barrel does .38 degrees of rotation cause?

Now we have to calculate using the distance from the fulcrum to the end of the barrel. Could be less but I will estimate about 8" due to angle which gives a 16" diameter or 16000 thousandths. That times 3.14 =  50,240 thousandths. Divided by 360, one degree = .139" of rotation. .139" X .38 = .053"

Conclusion: The barrel end will have risen or fallen (angled) by .053" when a clearance gap change of .010" is applied.

That's roughly the width of a dime. I doubt that difference could even be noticed. If the actual radius from the frame fulcrum to bore center is less than 1.5" the rise would a little bit more but not much. Measure it and see.

[Im2bent]

Hmmm I think you just killed off half the CAS population with that math 

[greyhawk]

Hmmm I think you just killed off half the CAS population with that math 

got me right between the eyes 

[RUSS123]

got me right between the eyes 

Ha very funny!

Simple math fellas! C=Pi x Diameter

Greyhawk, if anyone understands what I attempted to point out, it should be you. You introduced change in "point of impact" as a result.

By your statement, I knew what you were saying and I knew you understood that bringing the barrel further back to narrow a gap is going to physically angle it upward because it is in fact rotating on a fulcrum rather than coming straight back.

What I attempted to do, using the formula for calculating the circumference of a circle, was to only "put in perspective" just how much of an angle and physical rise there would be at the muzzle. Point of impact would be higher if your not compensating with the sights. I understand that as well. I just so turns out that it's not all that much.

I had a long conversation over the phone with Mike (45 Dragon) about this very subject along with cutting back on the frame as an alternative and many other things pertaining to open tops. Mike was trying to contact me to let me know my 1872 is almost ready to send back. Can't wait! I told him I wanted to make these calculations and post my findings.

If all that I wrote is too difficult to follow maybe I should rewrite it. If no one is interested, that's fine, I don't care.  I did these calculations for myself because I had the same thoughts as you and was curious.

[Im2bent]

Hey Russ just joking around so I don't start crying over that Walker. Who doesn't like geometry? What was Mike's feedback as far as cutting down the frame ? Did you have that done on yours? Inquiring minds want to know.

[greyhawk]

Ha very funny!

Simple math fellas! C=Pi x Diameter

Greyhawk, if anyone understands what I attempted to point out, it should be you. You introduced change in "point of impact" as a result.

By your statement, I knew what you were saying and I knew you understood that bringing the barrel further back to narrow a gap is going to physically angle it upward because it is in fact rotating on a fulcrum rather than coming straight back.

What I attempted to do, using the formula for calculating the circumference of a circle, was to only "put in perspective" just how much of an angle and physical rise there would be at the muzzle. Point of impact would be higher if your not compensating with the sights. I understand that as well. I just so turns out that it's not all that much.

I had a long conversation over the phone with Mike (45 Dragon) about this very subject along with cutting back on the frame as an alternative and many other things pertaining to open tops. Mike was trying to contact me to let me know my 1872 is almost ready to send back. Can't wait! I told him I wanted to make these calculations and post my findings.

If all that I wrote is too difficult to follow maybe I should rewrite it. If no one is interested, that's fine, I don't care.  I did these calculations for myself because I had the same thoughts as you and was curious.

Didnt mean to offend
so getting serious for a bit ------
I target shoot at 25 yards - woulda thought that 10 -12 thou cock up gap at the barrel face woulda been at least 3 to 4 inches poa at 25 yards ?
cutting 55 thou off a front sight should make enough impact difference you would notice it (on a 25 yard target) ? no ? yes? (I reckon off a rifle front sight at 100yards we gonna see it shift - pistol at 25 is same geometry)

My problem was/is I inherited my mothers eye for stuff not lining up right - she was a quiet respectful person but would walk into a strangers house and have huge difficulty in restraining herself from straightening up a picture that wasnt square - often couldnt help it -
So that tapered cylinder gap screams at me if / when I see it - and if I can see the taper - that thing is wrong and I am proly gonna fix it to stop the screaming. 

[RUSS123]

Hey Russ just joking around so I don't start crying over that Walker. Who doesn't like geometry? What was Mike's feedback as far as cutting down the frame ? Did you have that done on yours? Inquiring minds want to know.

On that score, I think Mike said that it's mostly not necessary but wasn't against it either. If your clearance gap is really really that bad, it's what I would want to do. In the beginning before Mike had my Open Top in hand to inspect, I introduced the removal of material from the frame because I believed there was no other way. I know he's not going to do that on mine yet still achieve a minimal gap.

Anyway, I don't recall him saying that he has ever had to do that. The slight angulation of the barrel was of no concern to him either and that's what sparked my interest to do some calculations. Like I said before, it appears to be very minimal. Besides, my 1872 has its sights on the barrel so there is no point of impact difference to be concerned with. Apparently a non issue for the most part anyway.

At what degree of error Mike would consider having to remove material from the frame, I did not ask specifically. Next time I talk to him I'll ask that question or he may chime in here to give that answer. We talked for over an hour and he loves to talk about this stuff, especially about the unique things he incorporates to the action to make it indestructible but he goes beyond that to explain it. I don't remember everything that was said.

You should give him a call to discuss what you think is best for your gun. I know Mike would love to talk to you about it.

The Arbor fit is most essential and is Mike's primary concern and second to that I would say is endshake. Mine may be somewhat of a different animal to a C and B because it has a gas ring bushing to take control of endshake regardless of the B/C gap size but he is intending on providing a minimal gap there as well. As he puts it, when he's done, my 1872 Open Top  will be something equal to that of a custom made Freedom Arms. To me, that's worth twice what I paid for it.

[RUSS123]

Didnt mean to offend
so getting serious for a bit ------
I target shoot at 25 yards - woulda thought that 10 -12 thou cock up gap at the barrel face woulda been at least 3 to 4 inches poa at 25 yards ?
cutting 55 thou off a front sight should make enough impact difference you would notice it (on a 25 yard target) ? no ? yes? (I reckon off a rifle front sight at 100yards we gonna see it shift - pistol at 25 is same geometry)

My problem was/is I inherited my mothers eye for stuff not lining up right - she was a quiet respectful person but would walk into a strangers house and have huge difficulty in restraining herself from straightening up a picture that wasnt square - often couldnt help it -
So that tapered cylinder gap screams at me if / when I see it - and if I can see the taper - that thing is wrong and I am proly gonna fix it to stop the screaming.

No, please, you did not offend, in fact, I laughed over your reply. Just how accurate my calculations are should be examined.

At 25 yards we could calculate the angle with a more precise measurement of the radius and see. Your target shooting 25 yards. As Mike explained, most CAS competition using open top pistols is done at close range targets where slight differences don't matter. You have a good point if I'm understanding you correctly. I understand your eye for stuff. Like you mother, I'm straightening pictures all the time at home myself. From what I know and I'm no expert, the only way to maintain original angular alignment of the barrel would require adjusting frame length equal to the amount of rearward correction for the clearance. That's just my theory. The thing is, can you safely assume that the original angular vertical alignment of the barrel is correct in the first place and in relation to the sights. As for sights, it depends on which gun we are talking about. The sights on my 1872 are on the barrel so naturally I wouldn't be concerned.

[Im2bent]

Actually I sent him an email regarding a Walker I am trying to tune and got no reply also no replies from anyone on the thread I started regarding that Walker so I don't know if I offended someone/anyone with all of my questions. I am starting to get the feeling I've been blackballed.

[RUSS123]

Actually I sent him an email regarding a Walker I am trying to tune and got no reply also no replies from anyone on the thread I started regarding that Walker so I don't know if I offended someone/anyone with all of my questions. I am starting to get the feeling I've been blackballed.

Probably because Coffenmaker and Mike the Dragon had already answered you as to what to do. Mike didn't answer my first email either because of being busy with personal matters. I call him and we spoke for over an hour.

Coffenmaker would seem to just have you shoot it with a .015" clearance gap and not address endshake as long as the Arbor/frame connection has been corrected but I don't want to put words in his mouth.  Mike, on the other hand would have you take it down to at least .003". The question of gap/clearance appears to be widely opinionated as to what best, including endshake. Mike and Coffenmaker don't always agree on this, according to Mike so it's no wonder.

Below, I hope to clarify some statements and instructions Mike gave you in this thread. Hope it helps and I don't want to miss interpret what Mike is saying either. I will state what I think he's trying to say based on conversations I had with him.

Understand that since the clearance we want to "adjust" is  above the arbor (remember the fulcrum ( barrel  lug/frame) is the "constant"  at this point)  it won't  be a 1:1 closure as you remove material from the button you installed on the arbor.

Here, Mike is just cautioning, pointing out that... the amount of material you remove from the button won't be the same at the barrel. It will be effectively more at the barrel because it has a longer radius from the fulcrum. Take it slow and check often. I said this before. This is what Mike means by it won't be a 1:1 ratio closure. Just a caution statement. Mike does not state anything against removing SOME material from the frame. My conclusion is that he feels it to be unnecessary but doesn't caution against it either. The last poster of your first thread did it successfully.

Furthermore, the clearances between the arbor and the arbor hole won't be totally eliminated just with the wedge installed. The wedge should impart tension to the  union of the barrel assy / frame assy which will give you a true reading of the bbl / cyl clearance. So, remove material from the button ,  install the bbl , drive the wedge in and measure the clearance. Repeat  until you reach your clearance spec.

First, Mike knows you have a .015 clearance gap issue and declares it unacceptable. Here, he's just stating the need to impart tension to the union of the barrel/frame assy for 1. to get an accurate reading when removing material and 2. also, "in general" for the union to be solid when all is said and done, just "another caution statement" My point only in relation to Mike's statement would be: Take some material from the frame if you see fit but leave enough material to impart tension with the wedge toward the targeted gap to the point where the arbor has a good solid union with the barrel assy.

When your spec has been met, there may be a slight pie shape to the bbl /cyl opening. You can clean it up by carefully filing  (probable slight adjustment of the clearance to regain any spec. loss). The barrel should end up with correct alignment (more or less) but the main thing is it will be the same each time you reassemble the revolver.

Here again, Mike expects you should be able to meet your targeted gap without mentioning any need for the removal of material from the frame to assist in meeting that spec. Mike says the barrel should end up with correct alignment, more or less. I would take his word on that but I'm not certain what that means.  His last statement is all about the arbor's solid connection with the barrel. It's the Main Thing to have. Your targeted gap may be his or what you feel comfortable with.

Commentary: Is it reasonable to at least remove some material off the frame if it makes you feel better and the job a little easier perhaps? I would say, go for it. Don't over do it though and adhere to Mike's cautions. I think you'll be just fine.