Touch hole behind Nipple too large?

[Larsen]

I've got a percussion rifle with a touch hole behind the nipple being about 5/64 or 3/32.

The nipple threads are gone so i would have to drill and tap a new nipple hole.


The question is if i place a 1/16 nipple in that gun and fire it, will there be a chamber between the nipple and the touch hole that builds up enough pressure to blow the nipple out of the gun?

Or will the nipple keep pressure inside the barrel as a bottle neck?

I'm not sure how i would fix the touch hole going into the barrel behind the nipple or if it's fine like that.

Sadly i have no pictures atm but the measurements are correct.

Any ideas suggestions would be welcome ty

 

[Zonie]

I'm having a problem figuring out exactly what your talking about. Perhaps it is a matter of the definition of things?

A "nipple" is a small piece that is screwed into the side drum or the breech plug in the case of a snail shaped "patent breech". It is usually about 5/16" in diameter and about 1/2" long. It has a tapered cone on one end for the percussion cap and threads on the other end, usually about 1/4" in diameter.
Inside the nipple it usually has a fairly large hole about 5/64" in diameter at the end of the cone and a very small hole somewhere between the end of the cone and the bottom of the threaded end. This small hole is usually smaller than 1/32".
The nipple is a expendable part. Usually the small, restrictive hole that is down inside it gets worn away from the hot gasses that are blown thru it.

When you say the "nipple threads are gone", are you saying the 6mm or 1/4" diameter threads are no longer there on the nipple or, is it the threads in the drum or snail that are gone? If it is the threads in the drum or snail the only good repair is to replace the drum or snail, or to weld it up, redrill it and thread it or, use a Heli-coil screw thread insert.

Small zones in the ignition area of a gun which do not fill with powder when the gun is loaded do not create a problem when it comes to pressures. If the screw threads in the gun and on the nipple are good, the nipple will not blow out. (There have been cases where people have screwed a 6mm thread nipple into a 1/4" threaded breech. When this happens, it is possible for the nipple to blow out of the gun when it is fired.)

 

[Larsen]

I'm having a problem figuring out exactly what your talking about. Perhaps it is a matter of the definition of things?

Hey thanks for your response!

What i'm talking about is the flash channel, going trough the barrel down to the bullet. I'm worried it's too big basicly.

Yes i've heard people saying helicoils, but wouldn't it be safer to just tap a bigger hole and go with a larger nipple rather than using a helicoil spring?

Edit: Oh and sorry, it's the threads in the drum not on the nipple. I'm not worried about the nipple at all i can just replace it. What im wondering about is the actual barrel flash channel.

 

[Larsen]

I would say the hole going down into the barrel is large enough to fit a match inside. This is the hole that is in the barrel when you remove the nipple, aka flash channel or touch hole.

 

[Larsen]

I guess i could just weld it shut and drill a new hole but before i do that i rather hear what you guys have to say about the sizes of these holes haha

 

[Zonie]

I'm putting a picture of several breeches here to help with what I'm going to say.

When I see the term "flash channel" I think of the angular hole shown in the CHAMBERED BREECH drawing up above. It connects the nipple hole with the bore in the barrel. IMO, these can't be too big. If anything, usually they are too small in most factory made guns.
The idea is, when your loading the gun, the closer the black powder is to the bottom of the nipple, the better. That's where you want it so the flash from the cap can light it instantly. When you load your gun with powder, you should have the hammer at half cock and make sure there is no cap left on the nipple.
With the hole thru the nipple to let out the air open to the outside, the air below the ball or bullet will be forced out thru the nipple. Along with it, some loose powder will be blown down thru the flash channel where it comes to a rest right at the base of the nipple. This is great.
If the hammer is down on the nipple or a old cap is still on the nipple or, the flash channel is too small, the loose powder won't be blown thru the flash channel so it will never end up at the bottom of the nipple. This can lead to mis-fires or hang-fires.

Getting back to the flash channel, a lot of guns had that drilled from the outside of the gun. When this is done, the hole is usually plugged with a set screw or as I sketched above, with a headed screw. Is this what your talking about when you say the threads are messed up?
If it is, then the best fix for the damaged threads is to go to a larger set screw or headed screw thread and drill and tap new threads for it. I am NOT speaking about the actual nipple threads here. I am speaking only about the threads and screw that is used to plug up the flame channel. (Many people call this a "clean out screw" by the way.)
If this is the area where the trouble is, and you decide to rethread it remember, the nipple threads are very close to the place where these threads exist. You do not want to damage any of the threads for the nipple so don't drill the hole for the new clean out screw any deeper than they must be to hold the screw.

When I was talking about using a Heli-coil that was only for repairing the threads that the nipple screw into. Not the "clean out" hole.

 

[Larsen]

I'm putting a picture of several breeches here to help with what I'm going to say.

Thanks a bunch! Then i'm not so worried about the flash channel then. I realise it's hard without pictures, so much different type of guns and i'm not very knowledgeable about them to call them out on the right terms.

I'll add a picture to make it more obvious what i'm talking about.

Thanks again!

 

[Larsen]

When I was talking about using a Heli-coil that was only for repairing the threads that the nipple screw into. Not the "clean out" hole.

Yeah that's what i thought aswell. It's only the threads the nipple screw into that's damaged.

 

[Larsen]

View attachment 16157

According to this picture it's definitely a chambered breech.

 

[SDSmlf]

Thanks a bunch! Then i'm not so worried about the flash channel then. I realise it's hard without pictures, so much different type of guns and i'm not very knowledgeable about them to call them out on the right terms.

I'll add a picture to make it more obvious what i'm talking about.

Thanks again!

Welcome to the forum.

So your gun looks like the one in the first photograph, not the second one?

 

[Larsen]

Welcome to the forum.

So your gun looks like the one in the first photograph, not the second one?
View attachment 16159
View attachment 16160

Hey thank you!

Yes, apart from it not having a vent hole on the side.

Edit: I can see in the pictures now that it would be closer to the nocks patented, it was the angle of the channel down the barrel that fooled me.

 

[Newtire]

Track of the Wolf sells oversized nipples to take care of problems like these. You could also drill out the threads, recap for a standard bolt, put the bolt in and cut it off flush after loctiting it into place. Then redrill and tap for standard sized nipple. I have done similar on an engine head and it worked to hold in a camshaft rocker stand for 150,000 miles. That's a lot of hammering. How much do you love this gun and do you have more time than money?

 

[SDSmlf]

If it’s like the one in the top photograph in my previous post, is it the nipple threads in the breech plug (open threaded hole in below photo) you are referring to?

And with nipple installed.

 

[Larsen]

Track of the Wolf sells oversized nipples to take care of problems like these. You could also drill out the threads, recap for a standard bolt, put the bolt in and cut it off flush after loctiting it into place. Then redrill and tap for standard sized nipple. I have done similar on an engine head and it worked to hold in a camshaft rocker stand for 150,000 miles. That's a lot of hammering. How much do you love this gun and do you have more time than money?

Well i do love it enough to go great lengths to fixing it for sure.

I mean using an original nipple would be prefered for sure, but using an oversized nipple if it's safer would be fine with me, i can live with that, thanks alot for your help ill go back here and read more later on

 

[Larsen]

If it’s like the one in the top photograph in my previous post, is it the nipple threads in the breech plug (open threaded hole in below photo) you are referring to?
View attachment 16161
And with nipple installed.
View attachment 16162

Yes correct, those nipple threads

 

[SDSmlf]

Maybe a close up photo of the hole with the damaged threads? Are they missing? Is it possible you have the wrong sized nipple?

If you are not sure how to measure nipple threads take the nipple to a hardware store and have them match it up. The manufactures information on the barrel (who made it) will also likely tell what the nipple hole threads are, or were when new.

 

[Larsen]

Maybe a close up photo of the hole with the damaged threads? Are they missing? Is it possible you have the wrong sized nipple?

If you are not sure how to measure nipple threads take the nipple to a hardware store and have them match it up. The manufactures information on the barrel (who made it) will also likely tell what the nipple hole threads are, or were when new.

Yeah my iphone is bust waiting for a new one so atm i'm abit out of a camera option otherwise id make it easier for you guys.

Yeah the threads are completely gone more or less, i would need new threads to screw anything in. I think the easiest thing would just be to tap a larger hole and use a bigger nipple.

 

[SDSmlf]

If the threads are completely gone, what size does the hole measure? That will determine what size thread you can step up to.

How accurately can you measure the hole size? Based on your earlier posts guess you are using fractional drill bits to measure. Will need a bit more precision than that (.015”). Ideally you could measure with gauge pins, but guessing you don’t have them. Next best bet is numbered and letter size drill bits. A 1/4-28 threaded hole for example requires a #3 drill (.213”).

Once you know the diameter, TOW sells 1/4-28 taps in +.005 increments up to +.025. For a reference example, to tap to the plus +.025 1/4-28 (.275x1/4-28) you would need a hole of .238” drilled with a letter B drill before tapping. You would then order the appropriate oversized nipple from TOW and be on your way. It is not recommended to just use the oversized nipple and ‘hope’ there are no issues (stuck or blowing out nipple for example).

If the above seems overly complicated and/or you do not easily understand it, suggest you find a competent gunsmith or machinist to make the repair. If this gets messed up much more you will have to replace the breech plug,

an even more challenging task.

I would not recommend a Helicoil repair for a nipple tread, although others may disagree. One major barrel manufacturer has had one or two barrel recalls for doing that exact thing.

 

[Zonie]

Whether a oversize nipple thread can be used or not depends on how badly the existing threads in the gun are damaged.

The oversize nipples for a 1/4" thread come in sizes that are .005 to .025 larger than standard. That is they go from .255 to .275 in diameter with a standard 28 threads per inch pitch.

These are made to replace nipples that have become loose in the hole. They are not made to fix cases where the old threads are completely stripped out.
In other words, if a normal nipple kinda rattles as it is screwed in, these oversize nipples are fine. If there isn't much if any of the old thread left in the hole, these oversized nipples should not be used. There won't be enough of the thread in the gun to engage the nipple with enough strength to be safe.

Put another way, a standard 1/4-28 thread has threads that are .016 tall. (.250 major diameter - .219 minor diameter = .031. .031/2 = .016 thread height).

If most of a 1/4-28 thread is gone so there are only traces of the old thread left, the hole, for all intensive purposes will be .250 in diameter.
If .275-28 threads are cut in that hole and a .275-28 nipple is screwed into it, the amount of thread engagement will be .0125. (275 major diameter -.250 minor diameter = .025. .025/2 = .0125 ). Basically, the new threads will have lost 20 percent of their engagement.

IMO, loosing 20% of the engagement might be OK for normal thread applications but when it comes to the high pressures and explosive speed of the pressure rise when the powder fires, it is not a good way to go.

That gets me back to the 1/4-28 Heli-coil as being perhaps the best option.
Any good gunsmith can install one of these but before he starts, if he is not familiar with black powder guns, point out that the new screw thread insert cannot cover up the flame channel and the 1/4" length of the shortest Heli-coil in that thread size might need to be trimmed slightly to keep the flame channel hole open.

 

[Okie Hog]

What brand is the rifle? That will tell us the size of the nipple threads.

As a mechanic I've used lots of Heli-Coils. I've long had all the expensive Heli-Coil tools but still don't like the things. About 50 years ago i discovered Keensert thread inserts. Simply drill the hole to a standard oversize, thread and install the Keensert.

i've repaired a few muzzleloaders this way using a 3/8X16 Keensert which has 1/4X28 internal threads.

https://www.carrlane.com/en-us/prod...all/key-inserts-thinwall-stainless-steel-inch