Locating barrel/breech plug in stock?

[TNHillbilly]

Is there some rule of thumb in where the rear of the barrel is located in relation to the primer pan? Seems like some are located so far forward, the vent hole would have to be drilled into the breech plug.

 

[Packdog]

I think you will get some differences of opinions here. The rule of thumb is to have the fence line up with the back of the barrel. Now that sounds reasonable and if you look at originals you will see that....however, todays brechplugs are longer than originals for safety reasons. That pushes the lock forward. Unless you want the vent hole in the breechplug face you have to move the lock forward. There are plenty of guns with the vent hole in the breech face apparently with no ill effects. I think you can find originals done that way also.

 

[William Joy]

You are correct. However I feel that the TH should be in front of the plug and a plug in 0.550 inch should be long enough.....
Choose the lengh of the plug, meassure the barrel and mark the future TH, match with the lock pan and you see where to inlet the plug/tang....
If you polish the front of the plug it will be way easier to clean....

 

[Zonie]

As was said, although it is not real Period Correct, the longer breech plugs almost forces one to place the lock a bit forward from where it would be on a original gun.

Basically, the face of the breech plug determines where the center of the pan will be.
If you are going to just drill a finished 1/16 inch size touch hole without a touch hole liner, the center of the hole can be about 1/32 of an inch forward of the face of the breech plug.
A flintlock rifle/pistol with just a 1/16 inch diameter touch hole going thru the barrel wall will probably give rather poor reliability. Lots of flashes in the pan but few complete ignitions.

If your going to use a touch hole vent liner, the center of the liner should be 1/2 of its diameter ahead of the face of the breech plug.
Using this value, a 1/4-28 or 1/4-32 threaded liner would be 1/8 of an inch ahead of the breech plug face.
These vent liners greatly improve the reliability of a flintlock and although most American made original guns don't have them, vent liners were in use in Europe in the 1700s.

 

[paulvallandigham]

Barrel makers leave extra threads in the back of the barrel for long breechplugs, and breechplugs are made longer than necessary, so you can remove whatever metal IS NOT NEEDED!

Don't hesitate to shorten that breechplug to fit the lock on your gun. This is particularly a problem with flintlocks. If you don't have the correct length of plug, you can't locate the vent 1/8" forward of the face of the plug, and have the vent in the center of your flashpan.

I have seen good builders cut or file off the excess length of the barrel to make the plug fit snug against the shoulder of the chamber forward of the threads in the barrel, and then fail to reduce the length of the plug enough so that the vent hole is properly located. The result is a groove cut in the face of the plug, where crud gathers, holding moisture that contaminates powder, and makes cleaning the face of the plug properly almost impossible. The groove mandates that it be picked clean between shots, which many shooters don't like having to do.

 

[TNHillbilly]

Good information! I am scratch building my first flinter, Lock, Stock and Barrel-i.e. unrifled, not vented. My only experience is with my 2 CVA flint pistols which are great fun. Just drilled vent holes. Now, while we're discussing this, what about going to far rearward,that is, moving the vent forward of the plug. What effects in this case?

 

[paulvallandigham]

As long as it doesn't go so far forward as to miss the powder charge, it will ignite. However, for safety reasons, you want to ignite the powder at the back of the charge, rather than at the front. Otherwise you get strange pressure spikes, and very inconsistent velocities. Considering the limitations on the designs of the locks available today, I don't think you can put the vent hole that far forward, anyway, and still be centered above your pan.

The reason for the 1/8" gap between the plug face, and the vent is to allow a place for crud to build up( in the corners) before it begins affecting your velocities, and SDV. Actually, much of the crud will burn out with the next shots, but as was seen in case of the barrel that ruptured when firing only blanks, crud does build up, and does not always burn away. A good plug face scraper used to get to the crud in the corners, where your cleaning patch and jag just won't go is always a wise tool to use periodically. If you use a liner in the barrel, you may even want to put that vent hole a bit further forward, so that your thread for the liner are not cutting into the treads on the plug!

The main deal here is to plan ahead several steps when building the gun.When positioning the barrel and tang in the stock, you have to keep in mind its position in relation to where the triggers, and trigger guard will be position for best comfort when shooting. That, in turn requires a knowledge of the Length of Pull, Drop at Comb, Drop at Heel, and Pitch of the stock to fit the shooter. Simply copying a gun you see in a picture, or examine may not work for you.

I found this out many years ago when I happened to have the opportunity to handle and examine closely a Tower Double Barreled, 12 Gauge Shotgun made in 1776, owned in a private collection. The barrels were 36 inches long, which I thought would make the gun horribly front heavy, based on other DB shotguns I had handled in used gun racks at Friendship, and the LOP was only 12 1/2 inches, when I thought I needed about a 14" LOP. Well, I put that gun to my shoulder, and to my great surprise, it balanced right on my forehand, and my eye was looking right down the rib of the barrels at the front bead. Whoever this gun was made for, he was a large man for the times, and had a long neck. The pitch and Drop at comb were substantially greater than I had seen on any other gun before then. I did not shoot the gun, of course, but I found that the balance of the gun made it feel much lighter than it was, when I mounted and swung the gun as if shooting a bird. The buttplate was nearly 3 inches wide, and very thick, indicating it was cast to provide a counterweight to the barrels to achieve that balance point. NOW, that is thinking ahead!!! :hmm: :hatsoff:

 

[Don B]

So, if I'm buying a pre-inlet stock, I need to know if it's laid out for a touch hole liner or not, right?

I ask because I’m awaiting a Chamber’s York kit to begin my first build. Their photo of the York rifle shows a vent liner, but an email from them mentions the possibility of a groove across the front the breech plug, which I want to avoid, and which I would think would not be an issue with a vent liner, so I have questions to clarify with them.

Regardless, does a builder have any options to add a touch hole liner if the barrel and lock have been inlet assuming no liner? I would think that removing 3/16" from the breech end of the barrel and breech plug face so that the plug's face moves back with respect to the pan would cause problems with the barrel inletting, no?

I suppose a related question is what options are there for adding a touch hole liner to a gun whose original touch hole has worn out?

Don

 

[Vaino]

Unbreech the plug and scribe a light line on the lock side flat denoting the depth to the shoulder {or plug length} and scribe another line forward of this line after you've determined the C-Line of the TH liner. Remove wood from the breech area so the TH line on the bbl is centered w/ the pan. The lock bolster should be at least w/in 1/32" of touching the bbl when doing this. The plug length on Rice bbls is approx. 17/32" {.53} and if the 5/16" TH liner OD is 1/32" in front of the plug face and the pan center to backface of the fence is 13/32" on a large Siler, then the dim. from the rear of the fence to the breech end of the bbl is 5/16". This locates the lock, trigger and TG too far forward from an esthetic point of view IMO, so I locate the TH liner further back which necessitates cutting into the plug face w/ a funnel shape. Haven't had any ill effects of any kind in doing so. Slanting the trigger rearward helps some in locating the TG slightly further back. Also installing a "White Lightning" TH liner really yields improved ignition and reliability....Fred

 

[Old40Rod]

So, if I'm buying a pre-inlet stock, I need to know if it's laid out for a touch hole liner or not, right?

Or to put it another way, you need to check everything to see how things line up when you get the parts and adjust things accordingly. :grin:

I'm working on a TN MT precarve from Pecatonica with the barrel channel inlet but not the lock. To get everything to work out right without having to do a bunch of reshaping of the lock panels, I decided to inlet the barrel back about a 3/16". This allowed me to inlet the lock plate in a good spot on the panels with the top center of the pan just a bit forward of the plug face.

 

[Don B]

Fred, I’m hoping to avoid any machining to the breech plug face, to avoid reported cleaning problems and because I don’t trust my abilities enough to start hacking at the plug. Could you accomplish the same thing by shortening the breech end of the barrel and then refitting the breech plug? (.40 C-profile Rice barrel)

Old40Rod, Did you move the barrel inlet back, or did Pecatonica do it for you when they did the initial shaping? If you did it, how did you handle Pecatonica’s existing inletting for the tang and rear face of the breech plug? Wasn’t the tang hanging out flopping in the breeze after you moved the barrel back?

Don

 

[Old40Rod]

Old40Rod, Did you move the barrel inlet back, or did Pecatonica do it for you when they did the initial shaping? If you did it, how did you handle Pecatonica’s existing inletting for the tang and rear face of the breech plug? Wasn’t the tang hanging out flopping in the breeze after you moved the barrel back?

I did it myself. Mine is a pre-carve from PR, with only the ramrod channel drilled and barrel channel cut. The stock and lock panels are rough shaped. Nothing else was inletted.

As it came from PR, the barrel channel was cut back to the breech area (perhaps "pre-inlet" might be a better term), terminating in a radius. The breech/tang were not inlet. I prefer to do that myself. Thus, I had to square it up the breech end of the barrel channel anyway to properly inlet the breechplug/tang and seat the barrel. The tang was no trouble to inlet and fit as I essentially had a blank canvas to work with in the tang area. I did have to bend my tang a bit, but it was straight to start with anyway, so it was going to be bent one way or the other

You are correct, moving the barrel rearward would be a more difficult affair if you have everything... breech, tang and barrel... fully inletted to start with... or if you are using a swamped barrel. Mine is a 7/8" .50 GM straight octagon.