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Space between cylinder and barrel (637)

Discussion in 'Handguns: Revolvers' started by fourdollarbill, Dec 13, 2008.

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  1. fourdollarbill

    fourdollarbill Member

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    Yesterday I shot a new 637 S&W 38+P with some reloads. The build up carbon ring at the end of the cylinder was just tall enough to rub the cylinder and I could not pull the double action as the drag was to great. It took a few minutes to find the problem. I think the barrel is too close to the cylinder. It looks to be about .010" or so. If I clean the carbon ring it will shoot 10 more before it touches again. Maybe I'll have to send it in for an adustment??? Does anybody know a correct distance between the two?
     
  2. Pistol Toter

    Pistol Toter Member

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    .004 -.006 is ideal, my carry Ruger Sp101 is @ .002. The .010 to me is pretty large even though I have seen .012, that's a lot. I would suggest you try a different brand of ammo. Sounds like what you are using is dirty. My 2 cents.
     
  3. fourdollarbill

    fourdollarbill Member

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    You are right about the dirty loads. I tried some AA#5 as a suggestion and it needs a lot of cleaning when done. I'm a little disturbed to here the .006" because my newer 642 has about .009 on the top and about .018 on the bottom. When I bought the 642 new I noticed it but it runs well. Also i'm a newbie with revolvers with 10 years of automatics under my belt. I'll try to get a pic of both peices and post them.
     
  4. The Bushmaster

    The Bushmaster Member

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    Go to a cleaner burning powder like W-231 and your problem will go away. .010, to some manufacturers, is excessive cylinder to barrel gap.
     
  5. Pistol Toter

    Pistol Toter Member

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    There is something wrong with that 642; it should be the same between the top and the bottom. Do you have an accuracy problem with that gun or does it not spew lead and powder. .018 is enough to pass an aircraft carrier through and not scrape the sides of the ship. LOL I've got 30+ year old S&W that don't go over .005 - .007 and most are on the lower end and down to .004. I don't have any trouble with the Ruger @ .002 but I use Remington or Speer or Federal mmunitions.

    PS: Sounds like you've got a misaligned yoke or the barrel that needs to be removed the cone . breech dressed, the barrel re-cut and threaded and properly reinstalled.
     
  6. Oro

    Oro Member

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    "looks" to be? It's dang hard to judge these by eye without a lot of experience at it. Read the sticky above in this forum by Jim March about the proper way to judge this. The feeler gauge set you will need is not common - it will require .001" increments from .002" to .014" or more.

    If this is a modern gun, don't fret, you can send it back to S&W for warranty repair. I agree with Pistol Toter that if you have measured the 642 correctly, that is not acceptable. Read the check out, measure it again, and if it's like that, then call S&W and they should send you a call tag to send it back to them w/o expense on your part.
     
  7. Pistol Toter

    Pistol Toter Member

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    Oro is correct in not being very common, but they can be found without a lot of effort. I have a set Of Mitutoyo that start at .001, .0015, .002 and right on up. The hole set must be close to .50" thick. Between them my Fowler vernier calipers and several Starett micrometers and Starett machinist scales, I can measure most anything. If you don't have the equipment let somebody else look at and measure the b/c gap also check the end shake, the barrel to cylinder alignment with a range rod and the yoke alignment. Revolvers are tough but hard or miss handleing / use can be detrimental to an otherwise fine gun. Sometimes S&W turns loose guns that ought not have left the factory and NOTHING is made like it used to be. There is little craftsmanship of pride left in the work place.
     
  8. svtruth

    svtruth Member

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    Could be

    the other end. My Redhawk was binding and I couldn't shoot it DA. Crud had accumulated under the ejection star and the rears of the cases were rubbing. Cleaning cured it.
    Good luck.
     
  9. fastbolt

    fastbolt Member

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    In the armorer class they teach to come in from the left side, at the top of the frame window, using Go/No-Go gauges to measure the cylinder gap. The acceptable range taught in the armorer class is .004" - .010".

    Conditions which might cause inconsistent or rough cylinder rotation could be an improper yoke line up, a loose/bent extractor rod or simply dirt/debris under the extractor.

    Just some thoughts for the sake of polite discussion, though. Don't have any way of knowing what's happening with your gun. Best to call and discuss it with S&W.

    S&W has excellent customer service if you believe your 637 requires service. Call them and discuss your concerns with them and see what they say. Ask to speak to a repair technician (if possible). They'll pay for shipping both ways for warranty repair.

    BTW, they go on their usual 2-week holiday break starting Dec 22nd.
     
  10. Old Fuff

    Old Fuff Member

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    Sometimes the problem is caused by leading, not carbon build-up. Back during the days when most revolver ammunition (factory and reloaded) used soft, swaged lead bullets cylinder/barrel gaps tended to be wider - in the .006" to .012" area. When the switch to high-performance loads using jacketed hollow-point bullets came along manifacturers' were pressured by customers to tighten the gap down to around .003" - .006" - which wasn't always a good idea.

    The gap should always be measured with feeler guages, and never eyeballed.
     
  11. fourdollarbill

    fourdollarbill Member

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    A lot of very good info. I did get a go no go gauge but it is just small enought to fit.(Crafstman) The 637 is a tight .006 and it will not slip into the .008. But Now my big problem is the 642. It measures .008 on top and the bottom is by far larger. I could not measure the bottom because the gauge is too wide but i'm guessing .012 to .015. Here is a picture of it. On my way back today I stopped at another gun shop and looked at another 642 and it looks exactly the same. The 642 shoots very well and holds very nice groups at close range. I think I will take your advice and call S&W.
     

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  12. .41Dave

    .41Dave Member

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    It looks to me like the forcing cone was not cut square. Definitely send it back to S&W, they'll make it right.
     
  13. janobles14

    janobles14 Member

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    ^ agreed.
     
  14. fastbolt

    fastbolt Member

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    Don't let your eyes fool you into doing something silly to the rear of the barrel. An improperly aligned yoke can fool you. Also, yokes are 'paired' with frames during production. You don't want to fool with one and damage it. Call S&W.
     
  15. fourdollarbill

    fourdollarbill Member

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    Obviously I will send it back. But can I ask. What will this forcing cone miscut face do? Is it dangerous? What will happen if the space is .015" or .020"? Just want to know for good information. ALSO... What would happen over time if I never noticed it? Kind of disturbing!
     
  16. fourdollarbill

    fourdollarbill Member

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    Holy cow! I just had the bottom measured and it is .026" gap. I just had a lesson from a very experienced gun smith. He said that may be the reason I had a squib load a while back when I switch to a shorter 125 grain bullet. He advised the shorter bullet crossed from the cylinder to the cone and that gap is opened more quickly and the powder did not stay under pressure long enough to fully burn. That explained all the unburnt powder when I had a squib. I feel more relieved to find out all this info today. It was driving me crazy. Thanks to you guys for keeping me on it -vs- my original thoughts of just ignoring it. Safety first.
     
  17. Old Fuff

    Old Fuff Member

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    Swing out the cylinder and look at the frame under the barrel. there could be a crack in the thin area. Also check the barrel forcing cone at 6:00.

    Another possibility is that the barrel hole drilled in the frame isn't straight, which would cause the barrel to be angled, top to bottom.
     
  18. Orange_Magnum

    Orange_Magnum member

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    When the gun becomes dirty from shooting the cylinder will turn less and less smootly on the transfer bar. The "stuck" cylinder will then lift and tilt, lean onto the end of the barrel, upon the hand poking the cylinder for a turn to the next chamber.

    If the barrel gap varies as the cylinder turns when the gun is clean you can sand the front of the cylinder, but only where needed.

    If the barrel gap is indeed too small on all chambers you can sand the end of the barrel.
     
  19. Old Fuff

    Old Fuff Member

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    I sure hope not! :eek:

    If the cylinder has developed end shake (back & forth movement) it will wear in a forward direction until the face of the cylinder hits the back of the barrel. If you remove metal from the back of the barrel the cylinder can continue to move forward. At the rear you are increasing headspace, and eventually the cartridges will fail to fire because of light hits.

    The correct solution is to move the cylinder backwards, away from the barrel. Then the barrel and cylinder will cease to rub.

    It wll come as a shock to some, but I understand that the factory is well equipped and has experienced workmen who can quickly take care of the problem. Why not use their services?
     
  20. Ron James

    Ron James Member

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    Gosh Old Fluff ! Are you saying that the people who made the gun know how to repair it?:)
     
  21. Old Fuff

    Old Fuff Member

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    Well it was a thought... :uhoh:

    The Old Fuff is a skinflint of the highest order... "Cheap" is too mild a word. :D

    Now if the job is done correctly some specialized tooling is required, and buying a +/- $30.00 shop manual can save you a lot of trouble. But all of this adds up to some serious $$$.

    In addition a little bird told me that this problem might require a barrel or frame replacement. Hardly anything I'd want just anybody too do on his basement workbench.

    If I play my cards right I can get the folks at Smith & Wesson to go over the entire gun and fix anything and everything they find is wrong.

    And they will do the entire job for free, and even pay the back & forth shipping costs.

    So that means I can save all of my own bucks for more important things, like ammunition, accessories - and even more guns.

    So I don't see it as a hard choice to make... :cool:
     
  22. fastbolt

    fastbolt Member

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    Yep, best to let the factory examine & repair (or replace) it at their expense. ;)
     
  23. krs

    krs Member

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    LOL! The factory? I don't see a need of that. If you've got a large crescent wrench you should be able to tweak the frame back to square, and a big pair of waterpump pliers to squeeze the two legs of the yoke together and you'll be good to go.

    But....it does look to me like the barrel/frame is straight enough but the cylinder is badly out of whack for whatever reason. Please send it to the factory and do not shoot it no mo'.

    I'm surprised that we don't see more like this considering the types of ammo that some people claim to be shooting from the little aluminum darlings.
     
  24. fourdollarbill

    fourdollarbill Member

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    I'm a pretty decent metal worker in some ways. I can tell the back of the barrel was cut at an angle. It may have bin ground by a machine or cut with a saw but it was not milled.

    The same Smith measured my 637 and at 6 oclock the gap is .011 and at 12 oclock it is .006". Every J frame I have is similar to this and every J frame I looked at new in the guns shops are like this.

    Are S&W assemblers using a belt sander to set this gap???
     
  25. Old Fuff

    Old Fuff Member

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    A lot can depend on when the revolver was made. Back when barrels were one piece, the shoulder would be adjusted so that when it was screwed tight the front sight would be at 12:00. If that left the cylinder/barrel gap too tight it was "corrected" with a file. How well this was done depended on the skill of the person doing it, and how much time he was allowed to do it. If the barrel isn't square the only way to fix it is to remove the barrel, put it in a fixture and turn it so it is square, and then take enough off of the shoulder so that it can be rotated another turn to take up the excessive gap. Notice that the gap between the underlug on the barrel and the end of the ejector rod is considerable. That isn't good but it does allow for adjusting the barrel as described above.

    These days the barrel is a tube that is threded in to a crush fit. Then a sleeve with the front sight and underlug is slipped over it. The sleeve is held with a nut at the muzzle end, and when everything is set the muzzle is faced off. In theory it should not be necessary to do any filing at the back end, but I'm not sure if they do so or not.

    The only good thing I can say is that they will fix it, and they'll do it on their dime.
     
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