Some assorted flintlock building questions

[H Wally]

Ok guys. First thing is that I am not a flintlock guy - past repairing locks I've never really had much to do with them. Never dealt with breach plugs, never built a flintlock, so these questions might be a bit on the stupid side.

This is the current situation:
Build involves a no-name .65 cal smoothbore barrel and no-name lock. Breech plug has been fitted to the point that the shoulder of the plug bottoms out against the back of the barrel and the face of the plug bottoms out against the rear of the chamber - dye on all points is rubbed off completely on all mating surfaces, so I think I've got a pretty good fit for the breech plug.




Have a couple problems.

1) The gun I have has a .50 inch threaded breech plug. I feel like this is a bit short, but I've never really inspected many breech plugs. Is this a problem?

2) I haven't drilled a vent hole yet. This is because the lock I have is not long enough for the pan to pass the front face of the breech plug without the mainspring and other parts of the lock sitting snugly against the back of the barrel.
I have two options:
A) Build a bigger lock, which probably isn't a huge deal but will delay my project by a month or more if I can get tools together before work goes crazy again.
B) Drill the vent through the barrel wall into the breech plug and then recess the plug to meet the vent. This is easier, but I'm concerned about exposing the threading directly to the vent hole and subsequent corrosion of the threads as well as the chance that if the plug advances slightly over the years the vent hole between the barrel and the plug will no longer align. Since the breech plug is a traditional style with only a short shoulder at the top forming the tang there isn't the option of drilling the touch hole into the breech plug behind the barrel in cap lock style.

SO - Am I being paranoid about drilling through the barrel wall and into the breech plug, thus exposing the threading to corrosion, or is this done now and again?


(And to avoid derailment - The barrel will be thoroughly proofed regardless of how things are done. I also would prefer to use these components, since they're what I have and don't want to spend much money on what is essentially a time spending project)

 

[trevj]

As far as threads go, we were taught, as Forces aircraft mechanics, that 3 full threads got you as strong a junction as you could get with a threaded fastener. The quality of the fit of the two sets of threads, and the material strength being appropriate were considered a given.

Cheers
Trev

 

[mooncoon]

I think about 5/8" is usual for the length of the threads, but some guns like brown bess s have surprisingly few threads engaged. I suspect you should be OK with 1/2"

I would drill the vent after inletting the lock rather than the other way round and I would also strongly recommend using a 5/16 vent liner for better ignition. As to building your own lock, I think you would be far better off to buy a Siler lock from TOW. I have built 3 or 4 flint locks (from scratch) and have not been completely happy with them. Their proportions are lot more fussy than for a percussion lock.

cheers mooncoon

 

[sail32]

Order a copy of the Track of the Wolf catalogue.
All parts are shown full size and you should be able to compare breech plugs.
Measuring in my older catalogue, the shortest breech plug was 11mm.
The types of threads are important but I can't help you there.

 

[H Wally]

As far as threads go, we were taught, as Forces aircraft mechanics, that 3 full threads got you as strong a junction as you could get with a threaded fastener. The quality of the fit of the two sets of threads, and the material strength being appropriate were considered a given.

Cheers
Trev

Thanks - that's a good little tid-bit. Personally I think the quality of material and machining are a tad suspect, but this is just a crash run and I'm just having fun with it so if it fails the proof

I think about 5/8" is usual for the length of the threads, but some guns like brown bess s have surprisingly few threads engaged. I suspect you should be OK with 1/2"

I would drill the vent after inletting the lock rather than the other way round and I would also strongly recommend using a 5/16 vent liner for better ignition. As to building your own lock, I think you would be far better off to buy a Siler lock from TOW. I have built 3 or 4 flint locks (from scratch) and have not been completely happy with them. Their proportions are lot more fussy than for a percussion lock.

cheers mooncoon

Hmmm - I'd been hoping to proof the gun before invest too much time in fitting the stock and lock. Realistically I don't think this'll be the prettiest or best fitted gun on earth in any event Gotta say too - if you haven't been happy with how your locks turned out I'm a bit concerned for my chances at success! You do some nice work!

Order a copy of the Track of the Wolf catalogue.
All parts are shown full size and you should be able to compare breech plugs.
Measuring in my older catalogue, the shortest breech plug was 11mm.
The types of threads are important but I can't help you there.

Thanks! I didn't realise they had full size catalogue entries.

 

[trevj]

Hmmm - I'd been hoping to proof the gun before invest too much time in fitting the stock and lock. Realistically I don't think this'll be the prettiest or best fitted gun on earth in any event Gotta say too - if you haven't been happy with how your locks turned out I'm a bit concerned for my chances at success! You do some nice work!

Worth considering, that of all the firing mechanisms used on guns over the years, the flintlock had the longest run to get the details sorted out. It's a pretty refined arrangement of parts, and not all the ways they work together will be obvious, as far as cause and effect of minor changes in the geometry goes.

Thanks! I didn't realise they had full size catalogue entries.

Yeah. Really worth getting at least one Track catalogue. the full size color pics are easy to work from if you want to build a lock. They can be copied and used as templates for rough inletting, too. But for the amount of work that goes in to one, they sell for silly low money for a complete, quality lock.

Cheers
Trev

 

[wr.sainsbury]

Good morning Hugh- My take would be your plan B and relieve the face of the breech plug in a broad V from about the centre of the bore narrowing down to the touch hole. Lock tite Red on the threads-set the breech plug and then drill, tap and install touch hole liner into the plug 2 or 3 threads which then locks it securely as set. Should be as secure as you can get using these older parts. Dry assemble first before loctite is used just to make sure the V lines up. Cheers, Bill

 

[sail32]

A good book is "The Gunsmith of Grenville County", by Peter A. Alexander.
Starting on page 63 is the chapter on installing a breech plug.
The face of the plug shoud butt up against the end of the rifling and the face of the tang should butt up against the end of the barrel with the flats aligned.