Latest dilemna

[Curt Larsen]

OK, I'm just finishing my southern rifle.  It has a 13/16 barrel.  I located the touchhole near the face of the breeechplug with plans to install a 1/4 white lightning liner.  The lock pan is keyed to this location.  I've drilled for the white lightning and it removed 1/16" of the face of the breechplug.  When tapped, 2/3rds of the white lightning is in the thickest part of the barrel leaving 1/3 in the breech cavity.  Four threads of the white lightning protrude into the breech area and need to be removed to reinstall the breechplug.  The leading question is whether 2/3rds of the fully threaded white lightning is safe with four threads of the remaining 1/3 of the white lightning removed and covered with the breechplug?  Or do I have to start over with a new barrel and shorter breechplug?  Arghhhhh!
Curt

[moleeyes36]

If I understand what you've described you have the vent liner protruding beyond the inside wall of the barrel.  If that's the case, regardless of how far in front of the breech face you are, you are going to have a devil of a time cleaning the bore unless you shorten the vent liner to be flush with the inside of the barrel.  I'll leave it to those more experienced than I to comment, but I don't see that you'd lose any strength by making the vent liner flush with the inside of the bore.  The threads engaging the barrel are the strength as I see it.  The threads that are inside the bore are only gripping air. 

Even at worse case you wouldn't need a new barrel.  You could shorten the breech end and have it re-breeched.  I may be missing something or over simplifying the situation, but that's how it appears to me.

Mole Eyes

[Curt Larsen]

Let me clarify it further.  The threads don't really extend much into the bore.  The problem is that 1/3 of the liner is in the breech cavity and must be removed for the breechplug to be refitted.  What that involves is removing 4 threads from the 1/3 that protrudes into the breech cavity leaving 2/3 of the liner with the remaining 8 or so threads which are holding in the thicker wall of bore.  So, will the plug be safe with 2/3 of the liner holding with 8 or so threads and only 4 threads holding the remaining 1/3 of the liner that protrudes into the breech and later covered by the breechplug?  Sometimes my explanations are a bit muddled I guess.
Curt

[E.vonAschwege]

Curt,
   I think I understand what you're getting at.  A few things to note:  It is not a safety issue to have your vent liner intersect the breech plug by such a small amount.  There is potential for fouling to enter the threads once you break that flat shoulder of the plug, but the general consensus is that it's not a safety issue.  In order to get proper alignment of the lock, we often have to place it in such a manner.  It's not perfect, but it does work. 

Second, Your vent liner should be shorted so that it does NOT interfere with the bore (top Red arrow). You need to be able to run a cleaning jag all the way to the breech face.  When I install a liner, I drill and tap with the breech removed, then I mark the depth at which I need to trim the vent liner.  If it intersects the breech plug then you can file a shallow dish into the plug face to intersect the liner (bottom red arrow).  Polish it like a mirror and you shouldn't have any fouling issues. 

The plug shouldn't need to be removed any more regularly than the vent liner.  Once the plug has been dished, reinstall it to its final place, and then install the trimmed vent liner.  Yes, the liner locks the breech plug in place, but that's alright. 

[Curt Larsen]

Thanks Eric.  I think you've got the picture.  The only thing is that I will have to shorten the hindmost 1/3 of the liner to allow for the breech plug to seat.  In your diagram you show the linier in the final dished portion of the plug.  In your drawing, extend the bp seat down from the top to intersect the liner you've drawn.  That's my situation.  As you screw the bp in you have to clear the portion of the liner until the dished area lines up with the liner.  This wouldn't bother me if it was a 15/16 or 7/8 barrel, but there isn't as much wall on the 13/16.   

[bob in the woods]

 I don't use vent liners on 3/4 in and 13/16th barrels . Like you said, there isn't much wall anyway, so a slight internal cone and that's it.  The Chambers liners have nice fine threads, so I think you're safe enough.  I have seen some with 1/4x 28 liners, and the barrel chamfered to take the liner…Makes me nervous. 

[kaintuck]

That's about like 1/2 patent breech

Marc

[RichG]

even if your 13/16 barrel is in .45 you'll still have 4 full threads with a 1/4x28 and 5 threads with a 5/16x32. if you're threads are good either one will be stronger than needed to keep your liner or drum in place.

[Curt Larsen]

Thanks for all of your tips.  I feel a bit better now and will go ahead and brown the barrel.  Next time I think I will forego a liner on the next 13/16 barrel I use.  Had I just drilled a 1/16 touch hole to begin with it would have avoided all of this.
Curt

[Dphariss]

Solves many problems. It allows all the threads to be sealed.
It does lock the breech but this is not important. The cavity in the breechplug needs to be BORE diameter not groove if a rifle barrel.

Its also possible to make vent liners smaller in diameter for setting them closer to the breech face. 10X32 and 12x32. This is a 12-32 vent liner.

Its fitted against a shoulder.


This greatly reduces thrust on the threads.
It looks like this internally.

Sizes down to 10-32 will allow a large enough cavity to allow filling with FFF powder. The thicker walls help prevent cracking which can happen with if they walls are too thin.

Dan

[Curt Larsen]

I guess what I should have done was to forget about being able to remove the breech plug and just threaded the face of the breechplug.  The tap drill did leave a 1/16 channel on its face.  I was afraid that it would force the tap forward and give me an oblong hole.  Oh well, live and learn.
Curt

[whetrock]

Curt,
You might have been able to thread the plug face, like you suggest, if you had used bottoming taps and only put the tap in to the depth of the barrel wall. That would have helped you avoiding having the tap ride against the side of the plug.

But I think the solution Dan has posted in his diagram is a really good one. The nice thing about it is that it would return the assembly to 100% integrity. What he is describing is not just a more-or-less satisfactory “fix” to a problem. Rather, it’s a well established method for breeching a barrel. It just happens to be the case that it would work well as a solution to your particular problem.

Dan's solution is also still available. Nothing you have done so far would prevent you from using the technique he has proposed. It would require that the breech be deepened and a new plug fitted, of course. I'm assuming that the tang has already been inlet, etc., but I'll mention that it is possible to saw off a tang and fit it to a new plug (pin, then weld in place, after the new plug has been fitted to the breech).

Whetrock

Solves many problems. It allows all the threads to be sealed.
It does lock the breech but this is not important. The cavity in the breechplug needs to be BORE diameter not groove if a rifle barrel.
…
Dan

[Birddog6]

I guess what I should have done was to forget about being able to remove the breech plug and just threaded the face of the breechplug.  The tap drill did leave a 1/16 channel on its face.  I was afraid that it would force the tap forward and give me an oblong hole.  Oh well, live and learn.
Curt

If you drilled it with the breechplug IN the barrel & it glanced off the plug face, you do have an oblong hole.  Now how much of an oblong is determined by the pressure that occurred.  If it barely hit, may be OK. But if it was pushing it hard, it could be an issue.  If using a White Lightening vent liner, the threads are very small, thus don't take much to mess them up.

This is a good example of one I received years ago & repaired.  When I received it, I took the vent liner out & this is what I found.  As you can see, part of the hole has no threads at all & it is the same on the opposite side.  Definitely Unsafe, IMHO.  The sad parts is the guy has built well about 150 rifles & it makes me wonder about all of them now. Of the  5 could check myself, one had bad threads (not full threads) 2 were OK, and 2 had the vent liner sticking in the bore so the jag could not get past it.    Needless to say, it was disappointing to see such work from a guy that is supposed to know what he is doing.....  



 What I ended up doing was remove the breechplug & relieve the breechface area, then redrill to next size up vent liner & retap to get full threads.  It worked out fine, just not what I like to see from a pro.  (or supposedly a pro)

Keith Lisle

[Curt Larsen]

Thanks for the new insights.  What I ended up doing was removing the rear portion of the liner (4 threads worth) that protruded into the plug area.  This cleared the seat for the plug.  Then I reinstalled the plug.  The plug face now covers the remaining rear portion of the liner and effectively seals it.  The rear portion of the liner is held in by four or so good threads.  I suppose if I get nervous in the future I can remove the liner and use a bottoming tap to try to get 4 threads worth into the face of the plug.  I've never tried to remove a liner like this, but I sort of recall an earlier post that discussed it.  I just noticed that I'm now classified as a "hero member".  Somehow I don't feel like much or a hero when I make problems like this for myself.

[whetrock]

Sounds like you worked out a solution. Good.

Just a brief reply to your last post...
You won't be able to cut threads into the plug face at this point. It has to be done at the same time the rest of the hole is threaded, or not at all. As Keith noted, if the drill runs against the face of the plug, it will make an oblong hole. And as you yourself mentioned, if the tap runs against the face of the plug, the tap will similarly make an oblong hole. If you try to add threads to the face of the plug after the rest of the hole has already been tapped, it will similarly damage the threads. So it’s probably best not to tinker with that at this point. Sorry if my comment about that above was confusing.

Regarding pulling liners… Yeah, they are easy to pull out by drilling out the touch hole slightly larger, and then using a bolt extractor, which is basically a hardened, tapered-thread screw with left-hand threads. As you twist the left-hand threads into the hole, it causes the liner to rotate counter clockwise, so as to unscrew it. If you want to see one, just google "bolt extractor".

[EC121]

If you get a nut with the size threads of the liner you are using and count the threads, you will probably find about 3-4 threads.  That is about all that is needed if they are cut well.

[Ryan McNabb]

Simple solution: don't use these touch hole liners.  Just drill a hole and get on with life.  You create so many problems and you solve none.

[Dphariss]

Simple solution: don't use these touch hole liners.  Just drill a hole and get on with life.  You create so many problems and you solve none.

If you shoot a FL very much eventually the simple hole will cost you. Been there done that. 3/32 vent is more likely to flash in the pan that a 1/16" built like this. And its far less accurate.


Now if you are on some range someplace or on a trail walk its an inconvenience. If you just drove 20 miles of bad of bad road (or 50) then an hour or 1/2 a day running and hiding and low crawling on an antelope  and THEN the thing flashes for no other reason than it just did. Its a MAJOR PITA.

Dan

[Curt Larsen]

I still like white lightning vent liners, but I probably won't use one again on a 13/16 barrel.  To keep that cone on the interior of the barrel I might try one on Snyder's tools for hollowing out the inside of the bore.  His tool looks simple and I have a couple of his sizes.  Next time I'll give it a whirl or twirl or whatever takes.  Thanks again for all of your comments.  The barrel is browned now with LMF and I hope to stain and  finish the stock later in the week.
Curt

[Dr. Tim-Boone]

Tom Snyder's internal coning tool works very well. I use it with an eggbeater hand drill and it gives great control. Doesn't take long!!

[David R. Pennington]

I'm sold on the Snyder tool. I've used it on the last couple builds I've done. I realize at some point I will eventually have to make a liner once I shoot the touch hole out, but that's a way down the road. I even used Tom's tool to cone the replacement liner I made for my old .50 the other day. I pulled the old liner (I thought it was a white lightening but found out different once I pulled it.) Threads weren't same, so I ended up making one out of a stainless bolt.