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Thread: Cylinder to barrel gap

  1. #1
    Boolit Master

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    Lightbulb Cylinder to barrel gap

    Have a KBI Pietta single action that has a .002 cylinder to brrel gap and it locks up after a few rounds, is it okay to file a few thousands off the barrel rather than facet he cylinder?
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  2. #2
    Moderator Emeritus/Boolit Master in Heavens Range
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    I wouldn't recommend it. First of all, I doubt if you have the necessary skills, or you wouldn't be asking this question. Secondly, you need to be thinking in terms of ten-thousandths at a time until the problem goes away, not thousandths (It's a lot easier to file a little more off than it is to file a little back on (BG)). And third, the really proper way to do the job is with a tool from Brownells, which will face the barrel off square to the axis. Your local gunsmith can use one to do the job right and probably for a lot less than it will cost you to buy the tool.

    If you decide to do it yourself anyhow, let me suggest you buy a burnishing file for the job. A burnishing file will polish more than file, and you have a lot better chance of getting a satisfactory job.
    Regards,

    Molly

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    I'm A Honcho!

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    Don't some of these revolvers have a base pin bushing in the cylinder ? Can you alter that bushing to move the cyl fore and aft?

    Bill
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  4. #4
    Boolit Master

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    A few rounds of what?

    If it is BP cartridges, you need more lube to keep the residue soft after firing. Try spraying it down with Ballistol, to keep it lubed up and avoid build up. Heck that might work if it is a smokeless issue, too. Maybe finding a cleaner burning smokeless powder would help some. Just a thought.
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  5. #5
    Boolit Master
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    I had a similar problem with a tightly fitted USFA when they still used Uberti parts. I thought it was powder trash in the barrel/cylinder gap, but it was not. At long last, I traced to problem to a powder trash being flow into the gap between the cylinder bushing and the frame boss. I put some 300 grit Clover lapping paste in there and cocked the cylinder a hundred times and the problem went away.

    I would not file on the barrel root. I might polish it a mite to make certain there were no high spots. I would use some 320 emery cloth backed by a file or another piece of flat steel.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  6. #6
    Boolit Master

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    Load is 250 gr cast boolit & 6.0 grs of Unique. I've shot this load for years in a Ruger but I can't get thru a full cylinder at the range.
    I dropped it off at the gunsmith to have them fix it.
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    Boolit Master

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    That's as good a solution as any.
    Keep us posted on what he finds- I'm curious.
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  8. #8
    Boolit Master

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    IF you feel you HAVE to have a larger gap Brownell's sells a piloted tool for doing this job. You DON"T want to have the end of the barrel anything but dead square and I don't know a heck of a lot of folks now days who can file square. I consider 3-4 thou as about ideal for smokless powder and 6 should do it for B/P with the right lube.

  9. #9
    Boolit Master

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    Gunsmith feels its heat related and that is causing the lock up. Gun will cock just fine until I shoot it then two or three rounds and it locks up.
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    Boolit Master

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    Does the problem go away when it "cools off"?
    3 rounds doesn't seem like enough rounds to heat a gun up- not even if you thumbed or fanned every one.
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  11. #11
    Boolit Master

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    Quote Originally Posted by Charlie Sometimes View Post
    Does the problem go away when it "cools off"?
    3 rounds doesn't seem like enough rounds to heat a gun up- not even if you thumbed or fanned every one.
    Not right away but when I get the gun home it seems fine, there are times I can do 6 but then no more then one or two and its a problem., it does lock up tight as a drum but you can't get the cylinder to rotate easy just by pulling the hammer back?
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  12. #12
    Boolit Master

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    Sounds to me like there is something in the mechanism shifting or binding up under recoil, then when you lay it down gravity and vibration take over and it clears itself. I just can't see 3 rounds causing that much heat retention or expansion on the frame and cylinder.
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    Moderator Emeritus/Boolit Master in Heavens Range
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    A question I should have asked right off, but didn't: Are there any rub / scratch marks on the face of the cylinder or the rear of the barrel? If they're binding THAT much, there should be some very obvious wear marks where they are binding.
    Regards,

    Molly

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  14. #14
    Boolit Master

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    I don't have the gun here now, but don't recall any rub marks. At first I thought the cylinder pin was pushed in to far, I pulled it out a tad where its susposed to be but didn't help.
    Problem is I bought this new years ago and its been a safe queen until a month or so ago, so no sending it back.
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    Boolit Master

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    Explain the situation to the manufacturer- they MIGHT take care of it just for the cost of shipping, or less. Never hurts to ask.
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  16. #16
    Boolit Master
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    Tom
    when you get the gun back get a feeler gauge the old type that was used to set the gaps on spark plugs
    check the barrel cylinder gap on each side of the barrel // note the space/// rotate one chamber do the same /// keep doing this for all chambers then check your notes and see if they are the same or if there is some differences
    i had a pard that had a vaq in 45 lc that had the problem you have
    after checking it i found that the barrel face was not square with the cyld
    and had to correct it for him plus open the gap a little cause he wanted it for bp shooting
    after correcting it shot fine
    but as others have said this is not something the avg person can do it is very hard to keep square and you will also need the tools to check for squareness
    a lot cheaper to have someone that has them do it for you
    mule

  17. #17
    Boolit Master
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    Ah yes...The Gunsmith! If he can't figure out what to fix, blame the heat. I hope you did not pay money for that tid-bit of wisdom!

    Go to your local Industrial Suppy house and buy a small can of Dy-Kem. It is machinist lay out fluid and comes in either blue or red. Give the cylinder and inside of the frame a coat of this stuff and go shooting. It will rub off where the parts are binding. This stuff can be removed easy with ordinary rubbing alcohol.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  18. #18
    Boolit Master JIMinPHX's Avatar
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    Quote Originally Posted by Tom-ADC View Post
    Have a KBI Pietta single action that has a .002 cylinder to brrel gap
    That's not really enough information for me to understand exactly which type of pistol you are talking about. Pietta Brothers make a lot of different pistols. KBI is (was) just an importer. I don't know which version(s) they imported. They type of pistol that you have will affect the best way to deal with a tight forcing cone gap. A picture might help.
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  19. #19
    Boolit Master

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    Box just says Liberty single action 1873, 45LC made in Italy.
    Don't know what else I can tell you?
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  20. #20
    Boolit Master JIMinPHX's Avatar
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    OK, 1873 Colt Army style single action cartridge revolver...that brings it more into focus for me. Numrich actually seems to have parts for those things. http://gunpartscorp.com/gander/products.asp?CatID=12492

    That's a model that I haven't messed with myself previously, so unfortunately, I don't have any solid information to contribute beyond some general suggestions for revolvers of that type.

    I would expect that the barrel threads onto the frame. If that is the case, then unscrewing the barrel & turning the forcing cone back a few thousandths on a lathe would be a good way to open up the gap. Facing the cylinder is another option, but it's more difficult to do a good job on that type of turning work. That model of gun may have something at the back of the cylinder that is holding the cylinder too far forward. I would look for that before considering any cutting. Being as I don't know that particular model, I can't recommend specifically what to look for.

    Sorry that I don't have more to contribute.

    .002" is very tight for a black powder gun. Smokeless powder guns are seldom much less than .004". Black powder guns usually have larger gaps because the powder residue builds up on them more quickly. Was that gun specified as being for Black Powder only? Or is it a smokeless rated gun that you just chose to shoot black powder out of? If it is a smokeless powder gun, have you tried it with smokeless powder? If so, did it give you the same problems? If that is the case, then this sounds like a warranty case to me. Unfortunately, I believe that KBI went under, so I'm not sure if there is anywhere that you can turn for warranty help.

    You might try putting a post up on the Charles Daly board if it is still in operation. The guys over there would know what the warranty status of KBI guns is.

    edit: scratch that last idea. http://www.charlesdalyforum.com folded up shop too.
    Last edited by JIMinPHX; 03-12-2011 at 02:30 AM.
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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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