touch hole liner PLACEMENT

[Don B]

There has been a lot of discussion about touch hole liners (and I’ve read it all) and I’m not here to re-hash the merits of with vs. without. But I think there’s one question I'm still confused about: assuming you’ve decided to use a liner, do you position the liner clear of the front of the plug face or drilled into the side of the plug?

I think the benefits of putting the liner in front of the plug are clear: the seal between the plug face and the breech shoulder is maintained and so there’s no worries about fouling and corrosion getting into the plug threads and the plug face remains nice and flat and easy to keep clean. The only downside to placement so the liner threads are in front of the plug that I can think of is the impact on the architecture. But how bad can moving the barrel back 1/4” be, so long as you’ve still got clearance for the lock bolt behind the breech plug?

To those of you who have decided to use liners, what factors have convinced you to put them where you do? I’m inletting the barrel in my first build, and need to decide where to put the liner and I can see no reason not to place it to clear the face of the breech plug. Am I missing something?

Don

 

[Allan Gray]

Your vent liner should be placed centered on the flash pan horizontaly, and slightly above the top of the flash pan where it meets with the frizzen. Some refer to this as the "rising sun" position.
Depending on the position of your lock, you may or may not be able to achieve this position. If your stock is pre-inlayed, you're somewhat married to the breech plug-to flashpan geometry.

If I had to choose, the position of flashpan to touch hole is more important than plug face to touch hole.

It is common to find the need to "notch" a cone shaped recess in the face of the plug to get a clear path to the touch hole.

 

[paulvallandigham]

Since the threads on your breechplug are there to help hold back the tremendous Pressure generated by firing the gun, the less damage you do to the threads, the better for the gun and the shooter.

For that reason, If you know in advance that you are going to use a liner, you want to position it ahead of the face of the breechplug, so that the threads of the liner do not cut into or butt up against the plug's threads.

As has been mentioned, however, there are problems that come about with kits, and stocks that have been inletted before you get them, and sometimes grooves have to be cut through the plug's threads to get the vent liner in a position where you can still ignite your powder charge. Most breechplugs made today are MUCH longer, in the threaded shank portion than traditional plugs were. In original guns, its not uncommon to find a plug that has only 3/8-1/2 inch of threads and length to it. You also see this short length in the plugs used in both original flintlock and percussion shot guns. barrels.

There probably is no very good reason NOT to shorten the Breechplug length when fitting it to a flintlock barrel, so that the touch hole and vent liner can be located properly, and not interfere with the breechplug threads. With today's steels, breechplugs are more capable than ever of withstanding the pressures generated in a flintlock rifle. For example, on a 5/8 x 18 Threaded plug, a half inch long threaded shank would still have 9 complete threads. And 3/8 " would leave you about 6 1/3 complete threads. As little as 3 threads can be enough, if old guns are an example, to hold the pressure.

 

[Zonie]

I never would suggest that one should drill and tap a hole into the side of the breech plug threads.

For that reason, I will say the vent threads should always be in front of the face of the breech plug.
Not by much, but still in front.
I generally shoot for a clearance of 1/32 inch between the vent threads and the face of the breech plug.

 

[Don B]

Depending on the position of your lock, you may or may not be able to achieve this position. If your stock is pre-inlayed, you're somewhat married to the breech plug-to flashpan geometry.

My stock is pre-inlet, including the channel for the swamped barrel. But I see no reason why I couldn't move the barrel rearward 1/4" to maintain the TH-pan relationship and still move the TH forward of the plug face. The barrel inlet is tight enough to allow this without gapping, I think.

Anyone out there who intentionally grooves the plug face want to weigh in? Ron Ehlert (and so presumably Jim Chambers) says grooving the plug face is the right thing to do. But in Peter Alexander's two books, he recommends the opposite.

So I'm still wondering: is there any reason to avoid putting the touch hole as much as 1/4" in front of the plug face?

 

[paulvallandigham]

I can't think of any reason to not leave that much of a gap between the face of the plug and your vent hole. That leaves room for crud to build up behind the vent, so its not blocking the vent during prolonged shooting matches. A long time gunmaker I know leaves at least 1/8" space in front of the plug( to the closest edge of the vent hole), when he installs the vent, or vent liners. The powder charge will certainly fill the space behind the vent hole adequately so that you get good ignition of the entire powder charge.

 

[agill]

I intentionally placed the vent liner so that I would have to machine a cone on the plug. I did this because Ron Ehlert and Jim Chambers suggested doing it. That said, I don't think it will affect the cleaning or ignition for better or worse. However, I wonder how much the pre-inletted barrel channel will be affected if the barrel is moved 1/4 inch aft? One way to find out for sure.

 

[Vaino]

All my flintlocks have the TH liners {White Lightnings} intentionally positioned so that they require a cone ground into the plug face. Personally, I don't like the looks of a LR that has the liner ahead of the plug face because the lock, trigger and trigger guard are all too far forward. Haven't had any repercussions w/ this funneling or coning.....Fred

 

[Birddog6]

Keep in mind that Jim Chambers & Ron Elhert are strictly PC & HC builders. That doesn't mean the old way was the best, it means that is how it was done during that period . Don't get me wrong, I have the utmost respect for both of them & have known Jim for years..... but that doesn't mean I agree with everything he does. :grin:

That being said, there is no way you could ever convince me that the breechplug threads & the vent liner threads intersecting will not leave a place for crud to build & rust to start. And if you cut a cone across the breechface & install a vent liner as you are suggesting, you have intersected those threads & left a void for a problem some day. Who knows when, 3 weeks, 3 years, e decades, 300 years, I don't know. But the void is there..

The ONLY way to seal that breechface 100% to the barrel is a 100% seal around it. Cutting a vent liner into that breaks that seal.

Now we get to the debate of how much rust is too much & how you gonna clean the BP crud out of those exposed threads in there & etc.

Personally, I would move the barrel back & not be PC & have a good seal at the breechface.

If you are going to intersect the threads & not seal it anyway, why even bother to go to the trouble of fitting a breechplug at all ? just cut it off, screw it in & go on..... :shocked2:

 

[Zonie]

If PC or HC is the BIG driver then the builder would not use a vent liner in the first place.

They would also cut off about 1/16 - 1/8 of the length of the breech plug making it about 7/16-1/2 inch long and remove material from the rear of the barrel to allow the new shortened breech plug to properly seal against the shoulder at the end of the bore.

The breech plug face would not have grooves, notches or any other disfigurements.

Now, with the barrels rear shortened, the short breech plug installed and the small vent hole drilled the lock could be located like it was done in the 1700s.

 

[Birddog6]

Now wait a minute........ :hmm:

What about all of those rifles that the vent burned out & they put a plug in & drilled the plug. That is a vent liner, tho it was not called that at the time. And what about the gold & platnum vent liners on the shotguns ?

 

[Zonie]

:grin:
Hot Damn! I plumb forgot about all of those gold and platinum lined liners! :shocked2:

:rotf:

 

[Birddog6]

:grin:
Hot Damn! I plumb forgot about all of those gold and platinum lined liners! :shocked2:

:rotf:

Uh..... huh !! and you thought you had me on that curve ball !! ha ha !!!!! :rotf: Now a knuckleball may have been a whoooooole different story...... :surrender: :rotf:

 

[Don B]

Personally, I don't like the looks of a LR that has the liner ahead of the plug face because the lock, trigger and trigger guard are all too far forward. .....Fred

But Fred, if I only move the barrel back, then the relationship of the lock, trigger, and trigger guard won't change. Right?

On my next build, I'm going to shorten the breech plug 3/8" and have the best of all worlds.

 

[Vaino]

The lock, trigger and TG relationship would be the same to each other....but the wrist starts at the breech end and the lock, trigger and TG would be more forward in relation to the wrist w/ a liner that doesn't infringe on the plug face.......Fred

 

[Don B]

The lock, trigger and TG relationship would be the same to each other....but the wrist starts at the breech end and the lock, trigger and TG would be more forward in relation to the wrist w/ a liner that doesn't infringe on the plug face.......Fred

Fred, I presume you're talking about the geometry of the wrist being forced to change to accommodate the tang and breech being moved back? Since my stock is a pre-carve, does what you said still apply? If so, is there anything I could do to reduce the impact of moving the barrel rearward?

Thanks

 

[Vaino]

Just completed a Chambers early Lancaster "kit" and the bbl is only set back enough so the White Lightning liner is into the plug face by 3/32". Perhaps it's just me and my paranoia on having the lock, trigger and TG too far forward, but it surely does lend itself to a pleasing lock/wrist architecture when those components are to the rear a bit. If your bbl is already set back so that the TH liner is forward of the plug face, so be it. Many builders do it that way and are satisfied w/ the results. Lately I've been filing the top of the wrist contour onto the bbl for 3/8" or so, so that might help some....Fred

 

[Allan Gray]

If your stock is pre-inletted for a swamped barrel and you can afford to move it back 1/4" without gap issues at the back or binding issues at the front,that would be great.

Another thing to consider moving it back that far is the adjustments you'll need to make to your tang length and tang screw-to-trigger plate angle.

I would personally rather have the vent hole over a small "cone" in the plug face than too far foward.

 

[rich pierce]

As we consider what they did originally: it seems there is an ASSUMPTION that when original touchholes burned out, a "bouche" or touchhole liner was centered where the old touchhole was. Folks think this would cause the need for coning the breechplug- not so. Generally speaking (excluding fine doubles etc) when original longrifles got fairly shot out, an inch or more would be cut from the breech end of the barrel to remove the old touchhole and eroded area at the breechpin (breechplug), the rifling would be freshed and the breechplug re-installed and a plain touchhole drilled as before. A touchhole liner was used only when the breech was not burned out at the same time. Whether or not that was perfectly centered on the old hole or might be scootched forward a tad- we don't know. Plus many "bouches" or touchhole liners when we can see them on longrifles do not appear as large in diameter as we use nowadays or as were present (in platinum or gold) on finer guns. Coning a slot in the breechpin is something I've not heard of much on originals. I wish we could get input from someone who has done a lot of restoration work.