doublegunshop.com - home Forums General Discussion DIY Gunsmithing @ doublegunshop.com Back Lock Hammer Gun

Hi all,
I'm looking for help on a back lock hammer gun. The problem is a wiggling hammer. I've tried shiming it behind the hammer and behind the lock plate. But, though it tightens the hammer, it also binds it. Does anyone know of a fix for this problem? Any help would be appreciated.

Is the hammer loose on the tumbler axle, or is the hole through the lock too big for the axle?

The axle moves the tumbler when you manipulate the hammer. The hammer is tight to the axle & doesn't move around when under the strain of the main spring (cocked). Does that tell me the lock plate hole has been enlarged from use? I would be surprised - its the left hammer and both barrels are cylinder choked. I don't think its been dropped on the hammer - no scars & mint. It's a .44 caliber shotgun & in excellent condition. Half of the color is still there & the twist barrels are about mint also (I think original). Its the lock plate hole isn't it, dang'it?

It could be ware on either the lock plate hole or the tumbler bearing surface or a little on both. Easiest repair is to shim the hole or the tumbler where it comes through the plate, also look at the bridal bearing hole for the tumbler this may also be enlarged. A good source of quality multi sized shim stock are Auto Engine feeler gauges.

So the idea is to shim between the lock plate and the tumbler - the shim holes being .002 or .003 larger than the axle so as not to bind it, and thick enough to strain the play out? I will check the bridle bearing hole. But even if it's one or both, you believe the strain won't hurt the tumbler, or move it out of place far enough to lose its purchase on the axle?

jebstuart,
Unless it affects function, don't try to "fix" it.
Mike

I have the distinct impression that the mechanics of a gun lock is rather a mistery to you, and may be best left too someone who more knowledgeable to remove the bearing ware. Just to make clear things clear, the hammer is fitted to a rotating shaft one shaft bearing is the lock plate its self with reasonable quality locks the bridle is the bearing for the other end of the shaft, with the tumbler permanently fitted to the shaft situated between the internal side of the lock plate and the bridal. Because of the force applied to the shaft by the main spring acting on the tumbler the holes in the lock plate and bridal over time ware also the bearings on the hammer shaft ware to some extent. To remove this ware in the bearing holes shims can be fitted, this being the quickest and simplest way.
To fit a slim metal bearing in to each of the holes it becomes a highly skilled job. I would go in to how that is done but I feel that few people have the required lathe to make said new bearings and the press to fit them because they have to be interference fit to make a high class job, also it is extremely difficult to fit bearings whose walls are fifteen thousands of an inch thick. Also a lathe is needed to skim the shaft bearings back to round then polish and burnish them.

I misunderstood the shim process, thanks for your knowledge.