Touch hole question

[Zonie]

IMO, 1/32" in front of the breech plug is asking for trouble.

If you use a 1/16" drill, it will just kiss the face of the breech plug but if your going to use a larger vent size or you are going to install a vent liner the drill bit (and tap if you are installing a liner) will hit the breech plug face.
Not only will that mark up the face of the breech plug but it will destroy the seal where the breech plug is seated against the face at the bottom of the breech plug threads.

The vent hole should be in front of the breech plug face by an amount that is slightly larger than the vent hole or the vent liner threads.

At least that's the rule I use when I'm building a longrifle.

 

[leverfred]

I will be 1/32" in front of the touch hole after drilling the hole.

 

[Flintandsteel]

If you're not using a liner, that will be ok. If you are, move the barrel back enough to clear the liner.

 

[leverfred]

No liner and it worked out just fine. I should be test firing later in the week.

 

[Desperate Lee]

I have a question for you guys .I have an old stock and barrel that I can mate an old lock to . Now when I do this the touch hole is behind and lower of the frozen pan . Can I plug the original hole and redrill another touch hole? That will make the new hole a little higher and forward of the original hole .This is a 44 cal barrel, new unfired, and I would love to save it.
Can send pics of need be .
DL




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[Black Hand]

I have a question for you guys .I have an old stock and barrel that I can mate an old lock to . Now when I do this the touch hole is behind and lower of the frozen pan . Can I plug the original hole and redrill another touch hole? That will make the new hole a little higher and forward of the original hole .This is a 44 cal barrel, new unfired, and I would love to save it.
Can send pics of need be .
DL

I'd move the lock to accommodate the hole and if this wasn't possible, move the barrel to fit the pan.

 

[Comfortably_Numb]

Why a walnut repair on a maple stock?

 

[Col. Batguano]

Don't forget to clean up the burr that is left on the inside of the bore after drilling through.

Functionally, I don't think it makes all that much difference how far in front of the plug face the hole is. It just has to be far enough in front so as to hit the powder column and not the ball.

Of course, if (meaning when) you dry ball, it's nice to have some space under the ball to fish some powder in there, and architecturally, it generally looks better to have the lock placed as far to the rear as possible. This is particularly true with the overly long plugs (historically speaking) that we use today.

 

[Alice1885]

One thing you can do if your touchole is low in regards to your lock mortise (lock location), I am referring to a flintlock lock build. You can deepen your pan on your lock, rather then lowering your lock. But the touchole should be somewhat centered in the pan of the lock referring to front to back direction. Best location is even with the top of the pan, in my opinion. But I have built rifles with the touchole a little lower, by grinding out the pan this does basically the same thing. And of course it's a great idea to always polish your pan and the bottom of the frizzen. Makes it much easier to wipe off the fowling. Good day !

 

[Desperate Lee]

Zonie
What is the fartherest you can be from the breech face and function reliably? I know you can't be in the patch but behind it anywhere? I
DL

 

[Zonie]

Zonie
What is the fartherest you can be from the breech face and function reliably? I know you can't be in the patch but behind it anywhere? I
DL

I can't give a very good answer that would cover all bases but, all of the vent liners I've bought from places like Track of the Wolf and Dixie have an enlarged counterbore in them which leaves about 1/16" of actual vent hole length.

These counterbore's are at least .156 in diameter (5/32") as I recall. (I couldn't find any spare, unused vent liners to measure them.)

Because this is the end of the liner that the ball sees it will provide a path to the area behind the ball where the powder charge should be if the center of the liner isn't too far forward.

When I install a vent liner I try to locate the center in front of the breech plug by an amount that is equal to the radius of the thread diameter + 1/32 of an inch to keep the thread tap from hitting the face of the breech plug. For a 1/4-28 threaded liner that gives me an ideal location of 1/8" + 1/32" = 5/32" (.156").

If the vent liner has a .156 diameter counterbore in it and I hit the .156 location exactly right, that puts the most rearward part of the counterbore .156 - (.156/2) = .078 in front of the breech face.
It also makes the most forward part of the counterbore .078 + .156 = .234 in front of the breech plug face.

Now, if someone dry-balled a .45 caliber barrel and rammed the ball all the way down to the hit on the breech plug face, the center of the ball where it contacts the bore would be .45/2= .225 in front of the breech plug so a tiny amount of the vent counterbore would be in front of the contact plane (.009) but almost all of the counterbore (.147) would be behind it.

This gives us something to work with. If the center of the vent hole was 1/16" ahead of the 5/32 distance I would like it to be, it would be 7/32 (.218) in front of the breech plug face. If it was that far forward, the distance from nearest part of the counterbore to the breech plug face would be .218 - (.156/2) = .140 from the BP's face.
That would be .225 - .140 = .084 behind the contact plane of the ball. Although that doesn't leave a lot of space between the counterbore and the rear area of the ball, I think it would be enough to get some powder thru to shoot out the dry ball.

Am I saying you should locate the center of the vent in a 1/4" liner, .218 in front of the breech plug face? NO. But I am saying, maybe using half of that 1/16" value I used in the above calculation might be a reasonable thing to do. If you wanted to use this 1/32" for a location tolerance, the center of the vent for a 1/4" thread liner would be .156 - .188 in front of the breech plug face.

 

[Col. Batguano]

"Zonie
What is the fartherest you can be from the breech face and function reliably? I know you can't be in the patch but behind it anywhere? I
DL"

Not Zonie but the answer is; that your patch and clean powder should cover the inner and most forward portion of the vent liner in the interior of the bore. So it's really a question of caliber and powder charge. A 30 gr. charge in a 32 cal is going to take up more vertical volume than the same charge in a 50. In order to allow the greatest flexibility in loads (meaning the lowest possible) most builders put the vent as close to the plug face as possible, and so as not to mess up the step for the plug. Obviously a 1/4" vent liner is going to take up more vertical space in the bore (needing more powder volume) than a 1/16" simple drilled-through hole, so that will have to be further forward.

You should be planning for this 1 way or the other when you lay out your lock location early on in the build.

 

[Sidney Smith]

I was curious after reading some of these posts, so I went to my work room and laid the touch hole liner in the pan of my flintlock in order to double check where I had placed the lock. The rear portion of the threads on the liner are maybe 1/32 of an inch in front of the line I have drawn on the barrel indicating where the breech plug face is. I had measured this distance on the piece of dowel I was using to insert into the breech area when I was working the breech plug into position. This then puts the touch hole itself about 2 1/2 to 3/16ths of an inch in front of the breech plug face when everything is said and done. This is on a .32 caliber rifle, so the powder column will easily cover this area by a good margin.

I'd think for someone worrying their touch hole will be too far forward, even in a larger caliber rifle, you'd have to be real far forward before you'd have to worry about the patch interfering. Surely less distance than in a small caliber rifle, but still you'd have to be very far forward, probably to a point that the lock position would be so out of place that nothing would work properly. The trigger would then be affected because the sear bar would be too far out of whack, etc.

 

[Col. Batguano]

Yeah you understand things. The main benefit of putting it as far back as possible is to let you use as small a charge as possible, AND, if it is behind the ball ogive, let you fish some powder in there through the TH WHEN the inevitable dryball happens.

A 1/4" vent liner + 1/32" forward of the plug face will put the center of the hole about .150" forward of the face, which will be tough to fish some powder in there with a .315" ball (.177 radius to the ogive, plus the patch thickness). That would be particularly true with a plain 1/16" hole bored straight through. With the cone on the inside of the TH liner flaring backwards some, you probably will be able to get enough in there to shoot a ball out if you're patient and persistent. You'll find that out when the time comes I guess. We ALL do!

 

[jrdavis]

This may have been discussed elsewhere but could not find it. I have a barrel but the touch hole is 3/8" after the breech plug, does anybody see a problem with ignition being that far away from back of barrel?

this seemes to have morphed into dryballing a ball instead of touch hole placement that being said the two books I have both seem to indicate that 1/8 in front of the breach plug and just above the center line of the pan is the best place for the touch hole ...I should think you could drill it out for a liner and move it to the rear a bit so the new threads cover the old touch hole... you did not say the size of your barrel there are only 3 sizes of commercial vent liners being made; or you could make your own.