Flintlock fit tweaking on Lyman GPR: How to approach advise requested?

[Oil Derek]

Howdy folk.

Per title I need to assess if I can do a refit on this Lyman flinter or hand it off to a local pro builder.  This is NOT my rifle and while interested, I am not a LR builder.  I am interested in dabbling and getting my feet wet.  Thought this might be a good place to start. 

Said builder rehabbed 2 TC and this Lyman lock.  He was shocked by the carbon residue on the inside of the lock and said that the gun/lock was probably a time bomb waiting to happen.  I mated the locks to their respective rifles and tried to inspect them for fitment.

On the Lyman, lock plate and mortise is tight and flush.  However, the flash guard (fence?) at the rear of the bolster is contacting the breech while at the pan it is .015” gapped and at front of the bolster it is about.019”.  Clearly this was/is letting priming powder to get behind the lock.

So, are there any other “big picture” things I need to further look at?  Then, what ordered steps do I take to remedy?

Thanks for hanging with me on this potential saga.

[JPK]

I would inspect the lock surfaces that may come in contact with the barrel and deal with that if needed. Failing to find problems there the inlet that the lock sets in gets the same treatment. One or both are causing the problem.

[Oil Derek]

Okay, thanks JPK.  Maybe I should pull the barrel and look at the barrel channel too.

[Oil Derek]

Here is the mortise with Dykem Hi-spot blue showing.  Are these high spots in the center/breach area enough to keep the bolster from closing on the barrel?

[B.Habermehl]

Since you used feeler gauges to actually measure the clearance between the rear of the lock bolster, it appears that the lock bears pretty tightly at the rear of the mortise. A bit of wood removal would help. Think paper thickness. Refit with transfer dye as in Prussian blue or similar. Watch for false readings due to starting the lock into place unevenly, do not over tighten. Next I would expect you would see less imprint at the rear and stronger at the center nearer to the lock bolt. Work back and forth until the bolster fits solidly. At one point you may need to dress the front of the lock mortise the same way. Keep it up until your satisfied with the fit. This is not rocket science, it just requires a bit of thought and mechanical logic. Go slow and give some thought to each step. BJH

[J. Talbert]

Here is the mortise with Dykem Hi-spot blue showing.  Are these high spots in the center/breach area enough to keep the bolster from closing on the barrel?

I’m not sure whether I’m seeing the high spot blue correctly or not. I can’t say that I see any BLUE, but if the shiny parts are in fact of the blue spots, then yes, that could be enough to prevent the lock from seating properly against the barrel. I would want to inspect the gun with the barrel and lock in place to be sure, but from your description and picture the lock is apparently not sitting parallel with the barrel.  The lack of any blue at the front of the inlet would also seem to suggest this.
Without seeing the gun in person I can’t be certain, but it appears to me that to make the lock fit you will need to leave the tail as is and remove any high spots forward of the tail.
Good,luck,
Jeff

[JPK]

Use a LOT less transfer blue to get better view of what’s going on. Put it on then try to wipe it all off, it will still be enough to show contact. The shine and texture in your photo makes it clear that too much is used. Remember it won’t make the fit, it’s only to show contact.

[Daryl]

Nasty crack in there.

[Steeltrap]

Nasty crack in there.

Yup. Glue syringe, clamp in vise for a day, should be good to go.

[Oil Derek]

Thank you gentlemen, now we’re starting to get some traction.  Perhaps it’s the mechanical logic I’m lacking!!! That Blue transfer dope has got to be 50 plus years old and duly noted in using too much.  Given old eyes I thought more was better to some extent.  And yes, the very shiny spots sure the wet transfer marks.

At this point I’ve reduced the gap by half.  Jeff seems right that the lock isn’t sitting parallel with the barrel as the the gap at the nose of the lock bolster is still about ten thousands out from barrel flat contact..  I’m missing the obvious somewhere. I’m getting no more dye transfer that I can see which is odd, I would expect to see full dye transfer in the mortise if it made total contact.  I was careful to check sear and trigger action often and didn’t note any problems there.  I relieved the area where the coil mainspring runs.  What am I missing?

[rich pierce]

Total contact is never achieved. Any small high spot can prevent seating of anything being inletted. At this stage I’d be pulling it in with the lock bolts, not tapping it in for transfer. If the front lockbolt is cockeyed or binding in the hole it could be an issue.

[Oil Derek]

Hi Rich and thanks.

There is only one lock bolt on this lock and I have consistently used it to draw into the mortise.  I have given the project a days rest so I can start with fresh eyes.  I was not seeing any dye transfer when I benched it last. 

I did not disassemble the lock but at the outset tried putting a straight edge to it and can’t see that the plate is warped or bent out at the nose.

Aside, are standard wood chisels used for this task?  I mostly used what I believe is a dental angled scraper typ instrument.

[taterbug]

The interference could be the lock and barrel at this point.  The lock bolster may need tapering at the rear to get it flat to the barrel.  Just make sure to keep the bolster surface flat from end to end.  you are getting into the last .010"-.020" of final fitting, so go really slow, and be certain you are hitting the problem spots.  Filing in one spot may make a high spot somewhere else.  I'm not familiar enough with that lock to guess if there may be metal to metal interference somewhere else too. 

as for tired eyes, really good light (more than one usually), and as much 'correction' as I can create is always a good thing for me.  I have trouble with 'visors' with only one focal-length lens, and find them too awkward too. 

I've started stacking reading glasses, one behind the other to create a 'bi-focal' setup.  Two 2.75x sets (for me), with one set being half lens height of the other.  I can look through the single set on the top half to see the workbench and tools, then look through the lower (both sets) to look at the detail work at about a 6-8" focal length.  Takes a bit to get used to, but without it I may as well be working in the dark.  Im sure I look a bit strange, but ain't nobody looking at me in the shop except the dog.  As long as he gets fed and gets to go outside a few times, he don't say much. 

[Oil Derek]

Thanx taterbug.  I was wondering about the lock bolster too.  The only contact with the barrel and breach is along the sweep of the flash shield(fence?).  I was hesitant to get extreme with metal work prior to inletting, which seemed to me the obvious place to start.  Didn’t want to royally screw up someone else’s gun.

And yes, I’m lighting deficient for sure.  I have 10x visor magnification which seem ok so far.

[JPK]

Show a photo of the inside of the lock and the breech end of the barrel where the lock touches. Seems to me the inside of the lock plate has a stud to except the lock bolt.

[Oil Derek]

Here are the two images JPK and thank you.

[JPK]

It appears that the stud that the lock bolt goes into is touching as well. I’d remove that wood so all the contact is on the flat of the lock plate. I see you cleaned up the bolster, so that’s good. As you get the plate settled in you may want to replace the vent liner so the screw slot isn’t making a path for the gasses to get under the lock.
https://i.ibb.co/pxRdH3f/1-F802920-FFD2-4-ECF-8-E48-AEABE3-DB8-DDD.png

[Oil Derek]

Great insight JPK concerning the vent liner. I would not have even considered that!  I did remove a fair bit of wood where the lock stud made contact.  With the blue transfer dye I can’t see where the lock is making contact at all now.  Maybe it has to do with the darkened walnut not revealing the dye and aged eyes.  Just last night I placed a small tab of painter’s tape on the wood where the lock bolt stud would mate and tightened the lock into the mortise, I don’t see any impression that the stud made contact.

I’ll look things over again today but I’m not seeing clues as to how I should proceed.

[JPK]

If your work area isn’t lite we’ll try a strong flash light focusing on just the inlet. Is the lock bolt bottoming out? If nothing is printing try tapping on the lock when it in place to seat it.

[Oil Derek]

Reasonably lit with a fair amount of natural light, but does need to be better for this type of work.  I have been using hi calibre tactical flash lights for close examination, which do the job wonderfully. 

I’m only seeing a tiny trace of blue dye at the very rear edge of the mortise.  The only other contact is at the front nose of the bolster on a 3/8”x 3/8” shoulder.  Not really sure that is a hang spot or if the lock shifts enough in assembly to transfer dye (lock inlet isn’t that tight fore and aft), if that makes sense. 

And yes, when hogged down the lock bolt is quite proud of the lock plate and does bow the plate in some at the middle. That relaxes to normal if the bolt is backed off to be flush with the plate.  My intent for over tightening was to get the dye to transfer, no such luck.

[Steeltrap]

Just tossing in my two cents, but the two pic's below may lay out the issue he's having?  (And I also think that's the reason the stock is splitting right where it's at.)

[Oil Derek]

Aye Steeltrap.  That was the first place I removed wood, in fact it was the most wood removed. I wasn’t too subtle about it on the third go.

I still don’t have a clue where the problem really is.  Almost impossible for me to see dye transfer anywhere; a pinpoint speck here or there.  Funny thing is, the top of the plate at the front of the bolster isn’t sitting as deeply in the mortise as the rest of the lock body (very noticeable) yet I’m not seeing any high spots there. Visually, it appears if that was inlet deeper or whatever the bridge that is keeping it from sitting in deeper (or rotating at the top) was addressed it would get close to contacting the barrel.  It is within  .006” at the flash hole and .010 at the front of the bolster now.

[Joe Stein]

Instead of transfer dye, try smoking the entire inside of the lock, guts and all, over a candle.  Sometimes the dull soot is easier to see than a shiny transfer dye.
Also, I think I see compressed wood fibers below the arrow that Steeltrap added.  That would be the lower, forward corner of the bridle. Looks like there is also some above the arrow, along the edge of the lock plate and on the raised portion just below the cutout for the bolster.  It doesn't look to me like the front of the lock plate is even contacting the wood.
Keep trying, you can do this.
-Joe Stein

[taterbug]

Since you've looked at the wood inlet a LOT, how about looking at some other parts for a bit.  It may not be the problem, but might help you get a different perspective. 

Just curious about how the lock screw is going into the lock plate.  Could that screw be pulling the lock to an awkward angle as it gets tightened? 

If you thread the screw into the lock with it out of the gun, does the screw stay square to the plate as it gets to the final position?  Or is it not square to the plate at all? Or is the hole in the stock not square to the plate surface, with the screw head and shaft being forced in the wrong direction as it gets tightened down?

Lastly, does the end of the screw hit the backside of the hammer when the screw gets fully tightened?  The screw may be pulling further into the stock each time you crank down on it.  Could be the source of the crack that is forming at the hole for the screw too... 

[Oil Derek]

Thanks Joe and taterbug.

I previously cleaned up the high spots that Joe addressed, but revisited.

I took Joe’s advice and smoked the $#@* out of the lock.  Thought it might be easier to examine the lock for wear spots than the mortise, for posting purposes.  One in your face high spot at the front plate and at fence and front of bolster.  Gasps still appear to measure the same. Tiny horse shoe line at at rear edge of the plate.  Not sure I want to mess with that as the nose needed to come to the barrel.  (That vertical white spot is oil reflection from the cup of the sear return spring.)

The lock bolt hole is well oversized and looks plumb enough when fit with the bushing.  It also looks good when started in the lock plate; when about 2 threads are showing through the face of the plate I perceive that it is leaning slightly toward the rear of the plate, but ever so slight.  The bolt does not hit the cock when fully tightened.

Thanks for the encouragement Joe, but me thinks I’m in a Mexican standoff.  Afraid to go too far as the mortise panel is a good 1/16” proud of the lock face now.  At what point does it become a total screwup?