BBL/Cylinder gap

M

Missoura Don

New member
Howdy all....A quick question about bbl/cyl gap...I read somewhere there should be a very slight gap between them...i have no gauges or other "tuning" tools as of yet.. but I cant even get a piece of paper between them...is this right....thanks for all the tips ive learned on here so far...you guys know yer s*** !!!
 
There has to be a gap or your cylinder will bind up on the back of the barrel. My Uberti Colt replica's gap is too small to get a piece of paper into when the gun is assembled but one will fit in there if it's put on the front of the cylinder before the barrel is attached. The paper then will pull out easily from the gap with some tension but not a whole lot.

You didn't say what model your revolver was or who the maker was. Some of the manufacturers have indifferent quality control which can translate to real problems in a Colt replica which requires precise tolerances between the cylinder arbor and it's hole in the barrel assembly. If you have a Colt replica and can tap the barrel wedge in until the cylinder won't turn freely, you have a problem. If your cylinder revolves o.k. now with a gap that's as small as you mentioned, it's probably just right.

Steve
 
Hey Steve...mornin to ya...Its the 2 piettas '51 navys I have, and I reckon there has to be some form of gap, or like you said,,the cylinder would bind, also, theres no scrape marks or anything like the sort on the front of the cylinder, just some machine marks, and I guess i have no control over that!!!..Thanks again Steve.
 
I've developed an opinion about the gaps in the percussion handguns. The gaps for them is better being more than a smokeless powder revolver.The gap is better suited to the fouling that accumulates on the cylinder face when it is a little larger than a smokeless powder gun. A rule of thumb that can be used is the old match book measurement.(I used to adjust the points in the distributor of my cars that way if it was needed when out on the road) Anywhooo, the match book fitting into the gap means its about as big as it should be and that size gap will allow the gun to keep cranking out the lead without binding from the fouling accumulation on the cylinder face. About .010-.012 I'd guess.
 
Wayner,
Not to hijack the thread, but.....
Did you use to use a dollar bill to dress the points too? I've done that a fair amount of times to get back home so I could change out the points.
I guess I'll have to check my clearances but so far so good. LOL
 
The gaps seem to run tighter than a lot of modern revolvers. I don't worry about them as long as the cylinder will spin as there is quite a lot of end-float built in the colts anyway (cylinder moving back and forth on the arbor.
 
Thanks for the input guys...These are piettas, '51 navys..There is no play whatsoever in the cylinders...tight as a drum both ways...and they seem to spin ok, maybe just a hair of drag...I was thinkin myabe fouling on the front of the cylinder was the problem with my first pietta...but i only fired 2 shots when it froze up!!..anyways..hopefully someday 'ill be able to afford one of them actuall colts...and as far as a matchbook cover slippin in between em....no way...cant even get a piece of postem paper through there...
 
MD,
Try Steve499's advise. Take the bbl. off and reassemble with a sheet of paper in fron of the cyliner(above the arbor and ubove the bbl, re-assemble and pull the paper out.
 
Pietta revolvers are made with the arbor bottomed in the arbor hole of the barrel.(the quality control of that process seems to be real good with the Piettas) That's good. That way a wedge can't be driven in enough to bind the barrel into the cylinder. The wedge could be driven in harshly and deform the metal of the wedge and the barrels wedge slot and the arbors wedge slot. Of course most people will not wack the wedge hard enough to deform metal but I've seen guns that were defected that way. Anywhoooo, the Uberti's I've seen don't bottom the arbor in the barrels arbor hole. The wedge can be driven in far enough to bind the cylinder with them. If the wedge is driven in too far the person can back it out a little until the cylinder turns and then a little more to allow for fouling accumulation.The looseness of the arbor in the arbor hole allows the barrel of a Uberti to close that looseness when the wedge is driven in too far by the barrel canting down at the breech end and canting up at the muzzle end and thus shoot higher(not good for the frames barrel pins or the holes for those pins in the bottom of the barrels). If a shim is fit in the arbor hole by placing it "on top" the arbors front end that enters the arbor hole then that looseness can be filled and the barrel then will not be able to cant to fill that space between it and the arbor thus not being able to bind the cylinder because the barrel contacting the frame at the bottom of the barrels lug stops the barrel rock solid just as well as if the arbor of the gun was bottomed in the arbor hole of the barrel. It just bottoms at the barrel frame junction instead of in the front of the arbor hole in the barrel. The width of the shim is determined by the difference in size comparing the arbors end that enters the barrel and the barrels arbor hole. A person can get a feel for sizing the shim since if it is too wide it will not go in.(the shim fills the space and cut widder makes it tighter and cut slimmer makes it more loose) The shim should actually be a little thicker than the space between the arbor and the barrels arbor hole because the shim material naturally is best suited for the job when it is made of a material softer than steel. Bronze,brass,"copper" or "aluminum". A shim cut with scissors from an aluminum pie pan works well with most Uberti's I've made a shim for. The shim is placed on the arbor sized about 1/4 inch by 5/8th's inch. It is kept from sliding backwards when the barrel is fitted on the arbor by the finger nail and a small screw driver so as to keep the shim fully inside the arbor hole. The barrel is driven on with a rubber mallet or some other composite that won't harm the muzzle of the barrel (wood)that gets wacked on to fully seat the barrel when a shim is on the arbor. The barrel is driven on and this "form fits" the softer than steel shim to fit the space between the arbor and the barrels arbor hole. The first time a shim is used the barrel goes on with a little difficulty. After that the shim is sized and the barrel goes on easier. The barrel will not be able to be removed by hand after the shim is placed. The guns loading plunger is placed between the chambers and the loading lever is used to lever the barrel off the gun for cleaning. Usually a person that uses the shim between the arbor and the barrels arbor hole doesn't go through the hassel of taking the barrel on and off to use preloaded extra cylinders. With the shim fitted the barrel won't be able to bind the cylinder and the gun will shoot less high and especially more accurately. The cylinder gap will usually be just about right when the shim is in place but if not other things have to be fitted properly. That's a whole nuther story though.
 
Mec,I'm wondering if people realize that to check the cylinder gap of the percussion revolvers they must do so by pushing the cylinder all the way back against the recoil shield so as to eliminate the forward thrust of the hand spring on the cylinder that is pushed forward by the hand spring? An overly stiff hand spring can cause a cylinder to bind when the gun accumulates fouling even if the cylinder gap is set properly since the spring pushes the cylinder forward. The overly stiff hand spring can cause drag on "the action" when the gun is clean also. Of course adjusting the stiffness of the hands spring is a nuther story.That tuning is "easier said than done". :eek: :D It's satisfying also as some people that have done it can attest to. There are some of those people right here on this forum.:D Cool.:p
 
Hey Wayner...thats a pretty good idea about the shim..Its just that I was raised and allways taught to NEVER force anything on a firearm...and the thought of pounding the muzzle, even with a wodden mallet...kinda makes me shudder,,,but hey, from what ive been readin here, you guys know yer stuff about these guns,,maybe ill run down the dollar store and buy me some pie plates,,,give yer idea a try...one more question on the wedge....Ive read and heard, that the right side of the wedge should never protude out further than the side of the frame...is this with all BP revolvers, or do certain guns have their own...style? thanks fer all the help guys...I havnt been to another BP site since I found this forum!!!
 
Avizpls, the barrel can be adjusted in different ways but usually it isn't needed. The barrel has to be determined to be seated properly on the arbor first thing. Bottomed on the arbor or in the case of most Uberti's shimed on the arbor to close the gap between the arbor and the barrels arbor hole. After that if the barrel is too close to the cylinder it can be relatively easy to adjust by filing(carefully) on the breech end of the barrel or better yet by using a piloted chamfer tool from a place like Brownells to face off some metal from the breech end of the barrel. That piloted chamfer tool would assure the face of the breech end of the barrel is concentric with the axis of the bore. If the barrel is too far away from the cylinder after the barrel is properly seated on the arbor and mated to the frame that requires more difficult gunsmithing.It is easily done if the person finds out the cylinder they have is a short one that fell through the quality control cracks. A new cylinder can be bought. If that isn't the case then the barrel may have been slipped through the quality control cracks after it was milled a little short on the forcing cone breech end. In that case if the gun owner finds that is true then a new barrel can be bought. Sell the old one on ebay.:D If the predicament isn't solved by either of those scenarios then it's off to gunsmith land for the gun whether it be the "kitchen table gunsmith" or the "pro". The barrel would have to be set back on the arbor and closer to the frame and the cylinder. That requires the bottom of the barrel to be milled or filed very judiciuosly to bring the barrel closer to the frame. The 1860 is better suited to this since the mating surface isn't a contour line that reaches to the top of the barrel like the 1851 types. With those the prettiest way to set the barrel back is to mill(or file) only the surface of the barrel where it contacts the frame that reaches to the top front edge of the frame. A little step will be on the barrels matting surface but it isn't readily noticable when it's done that way. The arbor may be bottomed in the arbor hole also and that end of the arbor would have to be milled or filed to bring the barrel back towards the cylinder equal to the amount that was milled or filed from the bottom rear of the barrel. A person would have to be able to measure the amount they wanted to take away from the bottom of the barrel and take that same amount away from the end of the arbor so when the barrel is set back the arbor will be properly bottomed in the arbor hole. Going very carefully here is a must unless the person wants to take a chance on taking too much off the arbor and then having to later add material to the arbors end to properly bottom it in the arbor hole. That is something that should be done to the Uberti's anyway to properly tune their percussion revolvers. It is best done after the barrel is milled or filed and set back the proper amount. Then a person may use some "color" on the end of the arbor to fit it to the barrels arbor hole properly. The color will show if itmis placed on the end of the arbor and fitted in the barrels arbor hole. When tha barrel seats at the bottom of it against the frame the removal of metal from the arbor should cease. The color, Prussian Blue machinist dye is a good one to use, should be transferred to the bottom of the arbor hole by the end of the arbor. If the color is put on properly and has no real depth to it and does not show at the bottom of the barrels arbor hole when the work is complete than the arbor is shown to be "too short". Add some weld to reshape the arbors end and start fitting it again or cut a little round piece of shimstock to be placed in the bottom of the barrels arbor hole. Seat it fully to the bottom of the hole and then check for the "color" again when it is seen that the bottom ot the barrel is seated against the frame. The piece of shim in the arbor hole should be cut from a harder steel shimstock so that it doesn't compress. If a softer shimstock material is used then the barrels mating surface at the frame should end up .002-.003 away from the frame to allow for the wedge to compress it and "form" fit it. Well, since one thing leads to another with this aspect of tuning the revolver setting the barrel back creates another problem that needs to be addressed.A person may decide that their wide cylinder gap really isn't too wide after all and just leave well enough alone and live with the wide gap when they realize what is involved in tuning the gun and setting the barrel back towards the cylinder a small amount. The arbor slot will also need to be set back as well as the barrel or a new widder wedge fabricated. The person in this case would need to take note of where the barrel is at it's rear of the barrel wedge slot compared to the arbors rear of it's wedge slot once the set back is completred. The wedge at the rear of the slot can not contact the arbor but must contact the rear of the barrels wedge slot only. The opposite is true at the front of the slots and the wedge should contact the front of the arbor slot only and not the barrels front of the wedge slot. If the wedge contacts the wrong thing at the front or rear of the slots then something has to be filed away to make things proper. Anywhooo, a new widder wedge can solve the dilema. Of course when that wedge finally wears out a new wedge would need to be fabricated again. A person may wish at that time that a new "factory" wedge would still fit the gun. Forseeing that would cause a person to want to do the barrel set back a different way in regards to the wedge and wedge slots and all. That is done by placing a bit of weld in the front of the arbors wedge slot and file shaping it back proper and file fittin a "new" factory" wedge. That actually only amounts to setting the arbor slot back about the same amount the barrel has been set back. One would hope that the barrel set back was done to a gun that had some latitude to drive the wedge in further and tighten the barrel to the frame without making a new wedge or settin back the arbor slot. Well. that's my "two cents".
 
Wow man.

just by the shear amount of text in there, I can tell you spent a great deal of time on an answer. Unfortunatly, I cant read it. You need a line break or twenty in there. :o

Thanks though, I got the jist.
 
Missoura Don, It wouldn't be considered "forcing" as much as "fitting". If you don't like that method of form fitting the shim then shimstock in different .001's can be purchaced and the right thickness found but trial and error unless you have the measurement tools to measure the arbor and the arbor hole and get a shim the thickness of the difference between the two parts. Also a wedge can eventually go all the way in as the gun wears on the wedge until it can go no more to tighten the barrel to the frame. After that when the wedge doesn't tighten the barrel to the frame a new wedge is in order. Avispls, I think I can guess what you are trying to say. Take your time and get a Colt revolver in your lap and seeing it and the parts lets your imagination print the whole picture. It "is" difficult reading about gunsmithing unless you have a gun and the parts to look at when you read. Am I guessing correctly what you mean?
 
no, I copied it all, and then added my own carrige returns. I reda it and its good. It was just the single solid block of text was litterally difficult to read.
 
Avispls. Oh. Now I believe I know what you mean.

Like this to seperate stuff.

And when it is appropriate to do so.


Do this. Do I have it?


I just figured out how to do that.:o Thanks for the heads up Bud.:D
 
haha, no problem. I was tryting not to come off as rude or anything.

Anyways, my cly gap is well over .016 :barf: I emailed SW to see what they say. I know the answer. I dont want to send it back again!
 
Hey steve, I took the '51 apart last night and when I reassembled it, I did your trick with the piece of paper before I put the barrel back on.....It pulled out with just a hair of resistant, so Im gonna take it the gap is ok. I put my campin flashlight (very bright) next the bbl/cyl joint, and saw no light...how can that be possible??..I know theres SOME gap there!!!!
 
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