touch hole location

[coyota]

i am at the point of inletting the lock on my 40 cal tennessee style and was wondering about the touch hole location. i'm using a white lightning liner and if i position the fence / flash guard at the back of the barrel the hole in the liner will be just ahead of face of the breach plug. if i do it this way and tap the hole for the liner won't i lose the seal between the face of the plug and the bore. ican put the liner ahead of the plug but it lines up better for the rear lock screw if its moved back. whats the better way to do this

[Dave B]

How long is your breach plug? some barrel have 5/8" plugs and it makes for a long distance for the fence to the back of the barrel. I have started shortineing my breach pugs on some of my builds to keep the fence closer to the back of the barrel. but still it is not a bad thing to keep the liner just ahead of the face of the breach so when you tap the liner threads you are just at the face of the breach.  I have yet to do this but it is possible on my next project that has the longer plug to make the touch hole liner seat against a shoulder drilled into the side of the breach plug and have the plug drilled down its center to the cross hole used as the pilot for the tap. This would be making a Nock type breach of sorts. I have done a few percussion breaches this way to good effect.
 

[flehto]

From the breechplug face  add 1/32" plus half the dia of the TH liner and lightly draw a line on the side of the bbl. When holding the lock w/ the pan centered on the line, the fence will be some distance from the breech end of the bbl....anywhere from 1/8" to 3/16 or so depending on the lock and plug length.. Nothing wrong w/ that. Because of the shorter  distance of the pan center to fence on some locks, the fence can't be in line w/ the breech end of the bbl w/o violating the plug face. If the threaded plug dim is too large, say5/8",  shortening and rebreeching might be necessary....or cutting into the plug face.

What size White Lightning liner are you using? Also what lock? Lately I've been using the 1/4 dia size which works just as well as the 5/16 dia. The 1/4 dia will give you less wood behind the fence......Fred

[coyota]

i am using 1/4 liner and l&r john bailes lock. i can put the liner ahead of the breach plug and still line up ok but it will put the rear lock screw kind of close to the rear edge of the lock bolster. in the gunsmith of grenville they put the center of the liner at the edge of the plug and file in a groove. but when a breach plug is installed you want a tight fit between the plug and bore. if the touch hole is moved back and a groove put in would'nt it compromise that seal?

[bgf]

Flehto's procedure is perfect.  It is ideal according to some to line up the back of the fence with the back of the breech, but not possible with all combinations of parts and not at all prevalent on originals, either, as far as I can tell.  Don't file a groove in the breech unless you have to, certainly not just to satisfy an arbitrary design instruction!

One additional note.  If this is your first or an early attempt, consider locating the touch hole center a little bit more forward, so that you can accommodate one size bigger liner, at least.  I, for example, leave room for a 3/8" liner even though I only use 1/4" -- that is probably overkill, but it means that I can fix a boo-boo with a bigger liner, either at the time of construction or later on without running into the breech with a bigger hole.  The extra 1/16" hasn't caused any problems, and I can go through two more sizes (5/16" and 3/8") before running into any conflict with the breech face.

PS.  RE: lock bolt at rear of bolster.  That can be a problem, esp. with the short bolster on the Bailes and Egg locks (the stirrup requires clearance).  As long as it is a good hole, it will hold, even if it is close to the back of the bolster -- I don't think you'll have much choice, anyway.

[coyota]

thanks for the replies. i think i will keep the liner ahead of the plug and avoid puting a groove in the plug. this is my first build and i have been reading all i can find before the next step and so far things have gone good. i bought a precarve with out the lock mortise cut out. i have barrel pinned and ramrod tubes inlet and about done with shaping the forstock.