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IJ Topbreak Revolver cylinder hang up

Erwin0206Erwin0206 Member Posts: 30 ✭✭
edited April 2011 in Ask the Experts
Just replaced the cylinder and barrel on an Iver Johnson 32 short topbreak. Everything functions beautifully - tight action, perfect timing, crisp trigger and good return when dry firing.
But when cartridges are inserted, about every 3rd round, with the hammer fully cocked in SA or DA, the trigger will not release the hammer. If the exposed cartridge is pushed towards the front of the cylinder, the revolver fires fine.
Any suggestions?
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Comments

  • hrfhrf Member Posts: 857 ✭✭✭✭
    edited November -1
    Your info is a bit confusing: Was the gun disassembled and then the original barrel and cylinder replaced, or were they replaced with parts from another gun?

    And to correct the problem, are you just opening the gun and pushing in on the cartridges? If so, you may just have dirty chambers stopping the rounds from seating fully, and the cartridge heads are binding on the frame and stopping the cylinder short of full rotation.
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  • Erwin0206Erwin0206 Member Posts: 30 ✭✭
    edited November -1
    Thanks for replying, hrf. The barrel and cylinder are from another same-year IJ. I have thoroughly cleaned both the chambers and the extractor, including the cylinder recess under the extractor face to try to eliminate all possibilities of rounds not seating properly.

    The cylinder actually does rotate and lock-up completely, but then the trigger will simply not pull.
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  • hrfhrf Member Posts: 857 ✭✭✭✭
    edited November -1
    quote:Originally posted by Erwin0206
    Thanks for replying, hrf. The barrel and cylinder are from another same-year IJ. I have thoroughly cleaned both the chambers and the extractor, including the cylinder recess under the extractor face to try to eliminate all possibilities of rounds not seating properly.

    The cylinder actually does rotate and lock-up completely, but then the trigger will simply not pull.


    The mixed/mismatched parts are no doubt the problem. The headspace may be too tight causing the cartridge heads to drag, or it may be locking the cylinder slightly out of alignment.

    Your statement "If the exposed cartridge is pushed towards the front of the cylinder, the revolver fires fine" is still not clear: Are you simply opening the gun and pushing in on the cartridges and then when closed again it fires OK?
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  • Erwin0206Erwin0206 Member Posts: 30 ✭✭
    edited November -1
    Detail - while the revolver remains closed and in this trigger-locked up condition, if I push forward on the cartridge on the left side of the cylinder through the narrow gap between the cylinder and breech, it allows the trigger to then fire the revolver. There is no cylinder movement when this happens, but this cartridge is usually slightly backed out of the cylinder, and I can feel a definite click when I press it forward. This is the cartridge position next to the hand, so I suspect it is binding against the hand.
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  • hrfhrf Member Posts: 857 ✭✭✭✭
    edited November -1
    quote:Originally posted by Erwin0206
    Detail - while the revolver remains closed and in this trigger-locked up condition, if I push forward on the cartridge on the left side of the cylinder through the narrow gap between the cylinder and breech, it allows the trigger to then fire the revolver. There is no cylinder movement when this happens, but this cartridge is usually slightly backed out of the cylinder, and I can feel a definite click when I press it forward. This is the cartridge position next to the hand, so I suspect it is binding against the hand.

    Does it work OK unloaded? (Also while unloaded or with empty cases check bore and chamber alignment in fired position with a bore light.) Maybe there's a burr on that side of the hand or on the recoil face of frame; try blackening the cartridge heads and the hand with a sharpie to see what's binding.
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  • Erwin0206Erwin0206 Member Posts: 30 ✭✭
    edited November -1
    Completely unloaded the revolver operates perfectly. The trigger lockup problem occurs identically with either live rounds or empty cases, and is about one round of every two or three. Manually testing the bore for problem alignment with a bore light and gauge reveals no problems. There is no evidence of any lead shaving, and the weapon fires tight groups at 25 feet with no flyers.

    I can detect no burrs on either the hand or recoil face. I just finished completely power cleaning and polishing all chambers to no avail.

    I believe my problem is mismatch between the barrel and receiver. Even though both revolvers are 1895 Iver Johnson 32 S&W serial numbers according to Bill Goforth's book, there are slight differences in the grips, and there may be just enough in the barrel/cylinder/receiver to produce a bind.
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  • hrfhrf Member Posts: 857 ✭✭✭✭
    edited November -1
    Why the swap, was old barrel or cylinder damaged? If you have the original cylinder assembly, try swapping the extractors.
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  • Erwin0206Erwin0206 Member Posts: 30 ✭✭
    edited November -1
    The old barrel has a crack in the forcing cone. I have tried swapping the cylinders to no avail, but haven't tried swapping just extractors since one is fairly tightly locked up and could not be unscrewed even with considerable force.
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  • 32 Magnum32 Magnum Member Posts: 820 ✭✭✭✭
    edited November -1
    Sounds like the rim of the next cartridge in line (to the left, the cylinder rotates "clock-wise")is hanging up on the firing pin bushing. That should be flush with the recoil shield. Check it out.
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  • v35v35 Member Posts: 12,710 ✭✭✭
    edited November -1
    Sounds like headspace problem.
    As I understand you, a fired case wont rotate into the firing position because of insufficient clearance.
    How much clearance is there between the back of a live round and the recoil plate when measured with feeler gages?
    A fired primer may back out slightly to take up that small clearance.
    The recoil plate is generally slightly forward of the rest of the recoil shield. This is to allow more clearance for fired case rims as the cylinder rotates
    Most all revolvers had fitted parts so you really can't expect to replace major parts without a little filing and fitting.
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  • Erwin0206Erwin0206 Member Posts: 30 ✭✭
    edited November -1
    First, many thanks to all of you for taking time to jump in. To answer a couple points:
    1. The lock up problem is the same regardless of using fired or unfired cartridges. Also, I have tried both Magtech and Old West Scrounger rounds, same result.
    2. The recoil plate has a very slight ridge along the edge of the firing pin assembly on the recoil plate, that could be binding.

    SHOULD I TRY FILING THIS SMOOTH WITH THE REST OF THE PLATE?
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