Barrel to cylinder gap question

[santee]

Ok. Is the gap between cylinder and barrel on these conversions supposed to be evident when the hammer is down, or when it's at half cock?
I can't see a gap until I put it at half cock, and then one sheet of paper will fit in there.

[Mako]

Santee,
When the hammer is down there will be no gap.  As soon as the hammer moves back there will be a gap.  The hammer spring provides the most force to push the cylinder forward but with even with the hammer back the hand still puts some pressure on the ratchet which pushes the cylinder forward slightly.  This is the reason you need to grab and push the cylinder back to get an accurate cylinder gap measurement.

Ideally you would measure the gap with the hand out of engagement with the ratchet.  You may have to have the hand out of the pistol if you are using paper instead of a feeler gage.  In trying to push the cylinder back and simultaneously hold the paper correctly to get a measurement you almost have to be a "three handed monkey" trying to keep the hand spring from influencing your measurement.  

If you are using paper get someone to hold the cylinder back for you and hold two sheets of paper with two hands and see if two fit.  If two fit, try three.  Hopefully only two fit.

Regards,
Mako

[Fox Creek Kid]

...you almost have to be a "three handed monkey"...

I learn something new here everyday.  Is that a technical engineering term? 

[santee]

Thanks, Mako. That helps a lot.

[Texas John Ringo]

Question: on an empty cartridge (conversion or otherwise)  revolver, with the hammer down, what is the hammer pushing against that changes the cylinder gap?

[Mako]

Question: on an empty cartridge (conversion or otherwise)  revolver, with the hammer down, what is the hammer pushing against that changes the cylinder gap?

Touche'  Ringo.  That is an excellent question.  I have been so wrapped up in C&B these last few weeks I missed the obvious.

In fact it I need to look at a revolver now to see the best position in a conversion.  With a two stage hand it just may be with the hammer down.  With a single stage hand I think it still puts some pressure forward pressure with the hammer down.  But with the Uberti two stage hands I think they are disengaged.

Sometimes I get too full of myself.

I'll check it out later with a couple of Uberti conversions.

Thanks for the tone of the question.  Have a great day.
Mako

[Coffinmaker]

Santee,

It depends on the type of conversion.  If we are talking about an original or 1851/60 copy that has been converted with NO gas ring, Barrel/cylinder gap will be about .004 to .008.  It will vary.
If the conversion is an Uberti, with a gas ring on the cylinder, first end shake has to be established at about .001-.002 then the barrel cylinder gap should be .004 - .006 for smokeless, in some guns as much as .010 for BP.  If you have a new Uberti conversion and barrel/cylinder gap goes away, end shake is wrong and the cylinder is going to bind.  It will bind real bad with BP.  Also, With correct end shake head space between the cartridge base and the recoil shield should be .004 - .006.
What kind of conversion are we talking about??  Makes it easier to give you a real good answer.

Ringo,

Depends on the above.  If it's a BP conversion without a gas ring the hammer pushes on nothing, check at half cock with the cylinder pushed against the recoil shield.  About .008 plus or minus a bit.
If it's a modern Uberti with a gas shield, doesn't matter.  The set up is the same as an S.A.A.

Coffinmaker

[Pettifogger]

Santee,

It depends on the type of conversion.  If we are talking about an original or 1851/60 copy that has been converted with NO gas ring, Barrel/cylinder gap will be about .004 to .008.  It will vary.
If the conversion is an Uberti, with a gas ring on the cylinder, first end shake has to be established at about .001-.002 then the barrel cylinder gap should be .004 - .006 for smokeless, in some guns as much as .010 for BP.  If you have a new Uberti conversion and barrel/cylinder gap goes away, end shake is wrong and the cylinder is going to bind.  It will bind real bad with BP.  Also, With correct end shake head space between the cartridge base and the recoil shield should be .004 - .006.
What kind of conversion are we talking about??  Makes it easier to give you a real good answer.

Ringo,

Depends on the above.  If it's a BP conversion without a gas ring the hammer pushes on nothing, check at half cock with the cylinder pushed against the recoil shield.  About .008 plus or minus a bit.
If it's a modern Uberti with a gas shield, doesn't matter.  The set up is the same as an S.A.A.

Coffinmaker

+1  You need to identify what it is you have.  People use the term "conversion" to cover a lot of different models.  Big difference between models with flat cylinder faces and models with gas rings.

[Mako]

Texas John Ringo,
You are correct sir, and I stand corrected.

I ran by my shop at lunch and looked at 4 different Colt's pattern "open top" pistols that are germane to this discussion.  I looked at a Uberti Type 2 "conversion," a Uberti Open Top, an ASM Type 1 "conversion" and a Uberti Army model I am using as the base for a true conversion to .44 Colt.  The last one still has a single stage hand and it still doesn't engage the ratchet even though it now sticks much further forward and at a different engagement angle with the new recoil shield added.

I read both Coffinmaker's and Pettifogger's comments, but I can't see how they apply (of course I have been wrong before).  It is true the gas shields on the Uberti pistols control the minimum cylinder gap, but the maximum we are usually concerned with is still controlled by the bearing face at the rear of the cylinder as it is pushed to the rear.  

So for measurement purposes with a cartridge revolver of the type we are talking about I believe (after being enlightened by Ringo) that the gap is best measured with the hammer down, or with the innards out of the revolver.  For Cap and Ball revolvers the directions I originally posted for Santee apply because the hammer either sits on the cone or prevents the cylinder from moving back to the bearing face.  

What you posted made sense Ringo, so I checked.  I also looked at a S.A.A., a '58 reproduction and a modern S&W and Colt D.A. revolver as well.  The measurement with the hammer back applies to C&B pistols.  There may be some other varieties that have hand pressure with the hammer down, but for our purposes and addressing what Santee asked about (remember this is the STORM board) I'm going to say cartridge pistols should be measured with the hammer down.

I know Pettifogger and Coffinmaker have considerable experience, perhaps they have seen a set-up that will be influenced by the hammer on a "conversion,"  I can't speak beyond what I have researched, modeled ,built or own.  They will have to address that.

So Santee, get someone to help you hold the revolver or hold it in a fixture or vise to allow you to use both hands in fitting those strips of paper.  Don't cock it all because as soon as you move the hammer back the hand moves up and forward.  It still may not even be touching the cylinder at half cock, but why even potentially bring it into play?

Best regards to you Ringo,
Mako

[Fox Creek Kid]

...and a Uberti Army model I am using as the base for a true conversion to .44 Colt...

Inquiring minds want to know. 

[Coffinmaker]

Mako,

With Uberti built conversions, with the gas ring integral with the front of the cylinder, the barrel/cylinder gap is controlled by end shake.  Also, Barrel/cylinder gap is also dependent on proper fit of the cylinder arbor into the barrel assembly. 
The first step is to insure the arbor seats fully into the barrel bore or a spacer added (Uberti are drilled too deep) to correct the arbor/barrel/frame fit.  Then you can establish correct head space, end shake and barrel/cylinder gap.  All of which can be effected by the gas ring.
Since most BP guns don't have a gas ring (Colt pattern guns), the only important part is the arbor/barrel fit.  Otherwise with BOTH type guns, barrel/cylinder gap will change every time the wedge is removed and replaced.  Plus, BP only guns have barrel/cylinder gap only when being cycled.  At firing, the cylinder face is up against the barrel.

Coffinmaker

[Mako]

Coffinmaker,
I'm not trying to be contentious, but your statement could be a bit misleading, you are sort of misusing when the term "end shake" applies.  It doesn't just apply to revolvers with a gas ring.  On any revolver the difference between the Cylinder Gap with the cylinder forward and the cylinder back is the "end shake."

I think what you were trying to say is that the forward cylinder gap (or lack thereof) is controlled solely by the cylinder face on a standard Cap & Ball revolver; but the forward cylinder gap on a revolver with a gas ring MIGHT BE controlled by the gas ring .  And I re-emphasize MIGHT BE.  If the gas shield is too short or the clearance cut for the gas ring is too long then it may serve no other purpose than to shield the arbor from the effects of the gases.

Only the rearward component of the cylinder gap should be controlled by the arbor fit to the arbor hole.  The forward component should be controlled by the gas ring to gas ring clearance cut relationship.

Off the top of my head I know the SAAMI specifications for .38 spl is .060-.074" ( Mr. Power  would run them .055-065" on PPC revolvers) That is the distance from the recoil shield to the rim seat.   Headspace is always measured with the cylinder forward.  In the case of a .38 spl.  you have a .014" tolerance which has to be distributed between end shake and the distance from the back of the cylinder to the ratchet bearing surface, or in the case of a recessed chamber the distance to the rim seat in the recess.

I'm very familiar with correcting the arbor length on a Uberti,  the only two I have that are unmodified are a pair of NIB '60s that I have set aside for another project.  I have a pair that was welded up, but found that to be too much trouble since I had to pull the arbor to turn the welded face.  I add a threaded spacer to the end of the arbor as I have been showing on my models of Uberti cap guns.

http://i627.photobucket.com/albums/tt358/Mako_CAS/1860/X-Section.jpg

http://i627.photobucket.com/albums/tt358/Mako_CAS/1860/SectionTop.jpg

http://i627.photobucket.com/albums/tt358/Mako_CAS/1860/Side.jpg

If you look at the first two images you can see the spacer threaded into the end of the arbor.  The third just shows the cylinder forward because the hammer is down.  This model has .008" of end shake, but in the parlance of Cap and Ball shooters, it has a "Cylinder Gap" of .008".

Have a good evening,
Mako

[Mako]

Inquiring minds want to know.  

You don't think I have all of those models of the conversion cylinders just for grins do you?    

I want some input from you on the correct loading gates, etc. for both Type I and Type IIs.  I was building a pair of Type IIs first because I am disappointed in the Uberti versions.  Type 1s would have a recognition factor because they aren't made.  I want the Type IIs because they would have the same sight picture, etc. as what I shoot now.  I want to make blank recoil shield blocks that could be further machined for any of the conversions.  That's what I want the input on.

I was going stronger on the work earlier because the Frontier Cartridge Gunfighter class was up for vote at the SASS 2010 Territorial Governor's Summit.  It failed even though it was 63% FOR and only 37% AGAINST.  It takes a 2/3rds majority (That's irritating we would have only needed about 12 more votes or proxies to carry it).  But you can rejoice Kid you can now wear your B-Western outfits and use a Burgess, just wonderful you can now dress in sequins but I don't have a class.  If they had passed the FCGF class I would switch to it.  I had been pushing all of the TGs I know to change the GF class to Simply Frontier Gunfighter and allow any BP revolver.  But I would take what I could get.

I'll finish a pair to use as my wet weather pistols.  Right now I have been carving on a '60 frame and barrel I bought from a guy who really messed them up.  A friend of mine told me about him and I called him up, he had lost the cylinder and most of the other parts.  He had the barrel and frame in a bucket.  I just bought a cylinder from VTI.  Plus I have a Pietta cylinder I got from the bargain bin at Cabellas for $35 last year.  I used the Pietta cylinder for some practice on the ratchet re-machining.  Found out the cylinder stop notches don't match up to a Uberti.  I think I'm just going to re-cut those deeper anyway.  I wanted to avoid making new cylinders and make actual conversions.

It's one of the many project I have half finished.  As I said the urgency has died a bit, I'm not sure if they will bring the FCGF back up this year or even the next.   I can dream though.

~Mako

[Kent Shootwell]

Perhaps some of you fellows could shed some light on cylinder bind for me. I'm working on a new Uberti R/M 1851 in 38 calibre. Haven fitted a new bolt and hand as well as corrected the arbor length then set the barrel cylinder gap to .008" and cut the forcing cone to 11 degree the mouth being .378"  I get binding after 10 to 12 shots with 16 grains of cowboy black powder under 1/20 cast 158 grain slugs lubed with SPG. It's clear to me that the binding is between the barrel and gas ring. Is there a cure for this? By the way this pistol shoots under an inch at 50 feet from a rest.

[Fox Creek Kid]

Mako, to save yourself sweat you need to start communicating with Ottawa Creek Bill as he built a 1st Model Richards conversion and made his own authentic cylinder for it. I have done the legwork in the search engine for you:

http://www.cascity.com/forumhall/index.php/topic,14860.0.html

http://www.cascity.com/forumhall/index.php/topic,11417.0.html

http://www.cascity.com/forumhall/index.php/topic,15302.0.html

http://www.cascity.com/forumhall/index.php/topic,11622.0.html

http://www.cascity.com/forumhall/index.php/topic,15370.0.html

Too bad the photos are long since gone. Send him a PM.

Kent Shootwell, are you LIBERALLY lubing the cylinder pin? I mean a LOT of lube.

[ndnchf]

Mako - where can I get one of those threaded spacers you used on the end of the arbor?  Do you make them?  I have an Uberti Walker that needs one. Thanks.

[Mako]

Mako, to save yourself sweat you need to start communicating with Ottawa Creek Bill as he built a 1st Model Richards conversion and made his own authentic cylinder for it. I have done the legwork in the search engine for you:

Kid,
You misunderstood me.  I don't need help with the set up, or how to fabricate the parts.  You have a keen eye for the authentic and point out deviations from the original patterns on a regular basis.  I actually have all of Bill's posts including the pictures.  If you want them I can dig them up and send them to you,  I saved them when they first came out in a PDF format.

Bill did a great job, but even he is still striving for 100%.  I know the obvious differences like the Type I extension over the cylinder, some of the differences in gate design, etc.  I just wanted a thorough list from a second party.  There isn't any reason to build another "almost" conversion at this point.  Besides,  I have an ASM Type 1 and I have a pair of Uberti Type IIs and  I used to have a pair of Uberti Army R&Ms

I have been collecting any attempts like Bill's, Wolf's and Flint's for years now.  I have had correspondence with Flint and Wolf and have been getting my ducks in a row.  Wolf has encouraged me to build them on Centaurs arguing the better materials and fit.  He's correct in that aspect and the pistols Nedbal built for him are extremely nice.  But, the markings and cylinder engraving would be off.

A word of warning though, this won't happen overnight.  This has been going on for about 4 years now, and I'm now swamped with my new business.
~Mako

[Flint]

ndnchf,

See the Pettifogger articles on making a spacer from the Dillon locator buttons.  Drill a hole in the end of the arbor matching the shank, and adjust the thickness of the head to align the barrel lug with the frame end.  Pettifogger's articles appear on the web and in the Cowboy Chronicle.

Also look at Mako's section views above to see how that button fits, look at the end of the arbor as it seats in the barrel.

http://www.theopenrange.net/articles/Tuning_the_Uberti_Open_Top_Revolvers_Part_3.pdf

[Mako]

Mako - where can I get one of those threaded spacers you used on the end of the arbor?  Do you make them?  I have an Uberti Walker that needs one. Thanks.

ndnchf,
I made some and had the last ones made as a favor.  The ones I made were too "precise,"  I tried to make them to the finished diameter, the drilled and tapped hole in the end of the arbor will never be perfectly centered so they ended up over hanging the edge and I had to reduce them anyway. However, I do make them to the finished length which means they are unique to each pistol.

I can explain the measurement process (which is a bit different than Pettifogger's that Flint gave you the link to) and provide you a drawing of the spacer if you wish.  I don't have any extras and I wasn't planning on making any in the near future.  

Flint directed you to  Pettifogger's fix using a Dillon shell retaining button.  It should work very well and require much less work and has an easy source of button blanks.  Pettifogger also had a concluding page in his instructions with the Dillon button that Flint didn't list:

http://www.theopenrange.net/articles/Tuning_the_Uberti_Open_Top_Revolvers_Part_4.pdf

I disassemble my pistols a lot because I use a cylinder loader so I wanted a spacer that I couldn't ever lose.  I had actually had a thin machined button glued into the arbor holes on my oldest set until I lost one of them and I don't even know how long it was until I realized it was gone.  I then thought about running a screw in from the front side to hold the button in place, Pettifoger had a similar idea, but used a set screw as a stop.  As you can see there isn't much material left in the barrel lug or room in the lever slot with the lever in the down position to clear a screw.  So I came to a solution similar to Pettifogger's.

http://i627.photobucket.com/albums/tt358/Mako_CAS/1860/leverdown.jpg

Let me know if you want the dimensioned  sketch.

~Mako

[ndnchf]

Flint/Mako,

Thanks for the info.  I previously read pettifoger's articles and they are very helpful.  But not having a Dillion button readily available and noticing yours has a threaded shank, I thought perhaps they were available, just needing to be trimmed as appriopriate. 

Another alternative I was thinking about is making a brass button without a shank, and simply soldering it onto the end of the arbor.  Then filing it to fit.  What do you think? 

BTW Mako, those cutaway images are awesome. 

Thanks!