retrofitting a vent liner

[Don B]

How do I deal with touch hole positioning when retrofitting a liner into a barrel? Assuming the original touch hole is ~1/32” in front of the face of the breech plug, as I believe it should be, if I locate the new liner concentric with the location of the original touch hole, the liner threads will run into the breech plug threads. On the other hand, if I locate the liner forward to avoid the breech plug threads, I’ll have obvious alignment problems with the pan and the new touch hole will be further forward of the plug face than it should be.

What am I missing here?

Don

 

[ol vern]

How do I deal with touch hole positioning when retrofitting a liner into a barrel? Assuming the original touch hole is ~1/32” in front of the face of the breech plug, as I believe it should be, if I locate the new liner concentric with the location of the original touch hole, the liner threads will run into the breech plug threads. On the other hand, if I locate the liner forward to avoid the breech plug threads, I’ll have obvious alignment problems with the pan and the new touch hole will be further forward of the plug face than it should be.

What am I missing here?

Don

You are not missing anything, but you realy do not know how far in front of the plug the touch hole realy is. Unbreach the barrel and drill & tap for the liner, file notch in the breach plug
if nessary to clear the new liner

 

[LRB]

The above would be your only practical choice.

 

[Don B]

The above would be your only practical choice.

That's too bad. I REALLY don't want to mess with the nice flat face of my breech plug.

Don

 

[Don B]

Unbreach the barrel and drill & tap for the liner, file notch in the breach plug
if nessary to clear the new liner

I suspect I don't understand exactly what you mean by notching to "clear the new liner". Do you mean filing away whatever threads in the breechplug would interfere with the liner when the liner is installed (after the plug is already in place)? I assume I would also need to extend this filing as a notch across the face of the plug, no?

 

[mazo kid]

Assuming the original touch hole is ~1/32” in front of the face of the breech plug, as I believe it should be, if I locate the new liner concentric with the location of the original touch hole, the liner threads will run into the breech plug threads.
Don

First thing to do would be to find out where the vent hole actually is in relation to the breechplug face. You will have to pull the plug to drill and tap for the liner anyway, so you MIGHT have to slightly notch the side of the plug for clearance. If the vent hole is ahead of the plug, you won't have to go into the face of the plug at all.

 

[William Joy]

If you take a liner which is not coned on the inside, you can take the breech plug off, drill and tap for the liner, install the liner, make sure it is flush inside and re-install the plug. You might need to recut the tread so the plug fits ( sometimes not nessessary- the plug will just clean it up) . Liner installed - and still a nice smooth plug face!

 

[Don B]

Thanks, WJ. The noggin light finally went on.

I'd want to use a White Lightning-type liner, though. I suppose I could install a non-recessed liner as you suggest and chamfer the outside to accomplish some of the claimed benefits of the White Lightning liner.

 

[paulvallandigham]

NO, you will not get the same benefits of the White lightning liner by chamfering the outside of the vent hole. You may move the priming charge closer to the main charge in the barrel doing that, but since its heat, and not flame that ignites the BP granules in the barrel, you are talking a microseconds in time saved to ignite the powder.

The benefit of the White Lightning liner comes from the parabolic cone on the inside, which focuses pressure and heat back towards the powder charge when its trying to escape out of the vent. This short delay allows pressure to rise FASTER, causing heat to rise faster, and powder to burn more efficience in a shorter amount of time. Its when the PRB or bullet begins to move forward down the barrel that the effect of the Parabolic curve on pressure is neutralized, and gases then come out the vent. A straight sided cone cannot do this, and a straight hole cannot do this. Only the Parabolic curved cone does this.

Remember that when these first came out, everyone-- I mean everyone--- scoffed at the claims. They they tried the cones. It works. Instead of scoffing, we are all now laughing at ourselves for not listening, and then thinking about what is going on. :rotf: :rotf: :hmm: :thumbsup:

 

[Don B]

The vent hole would have to ahead of the breech plug face by 3/16" (half of the vent liner threads major diameter) to avoid a thread interference, right? I've assumed that the vent hole should be as close to the breech plug face as possible for the best ignition, 3/16" seems like a lot, but maybe I'm making a mountain out of a molehill.

 

[paulvallandigham]

You want the back end of the vent hole to be about 1/8" in front of the face of the plug. That sounds like a lot, until you measure it. That space allows a place for some crud to build up without interfering with the igniting of powder in the barrel.

White Lightning liners come in a couple of diameters, so choose the one that will work best in your gun, taking into consideration the location of the current vent, the face of the plug, the center of your flashpan, the height of the barrel flat into which you will screw the liner, etc. The liners have fine threads, to increase the amount of threads that hold the liner in the side of the barrel. Make sure you use the tap they send you, or will sell you with the liner for threading the barrel for the liner. Take your time, and do the tapping correctly. Remove excess metal from the inside of the liner- that portion that is in the barrel. You want the liner to NOT extend into the bore, and obstruct your cleaning jag from reaching down to the plug.

Once you have the liner installed, you can back it out, temporarily put the breechplug back in, mark the thread that may( I do say "may") interfere with the liner. Since the plug has more threads than the liner will have at this point, grind away that spot on the threads to create a relief to allow the liner to seat all the way down in the barrel. You won't be removing much metal, and the work should not even be visible from the muzzle. That smooth, flat face you filed will be seen in its entirety.

 

[Vaino]

As was said before...remove the breechplug and determine how far the present TH is ahead of the plugface. If installing a White Lightning liner {1/4" dia. is the smallest} decide if you want to retain the present TH location w/ the possibility of having to grind a cone shaped relief in the plug face or relocating the liner center forward of the present TH center by 1/32"or so {would require a mill} and then grinding out the lock pan to suit the new location. You still might have to grind the cone relief, but not quite as deep. At any rate, the liner can't protrude past the plug counterbore threads or the bore. Because I don't like to position the lock,trigger and trigger guard so far forward because of trying to miss the plug face w/ the TH liner, I usually grind a cone shaped relief into the plug face to accommodate the TH liner and have never had any problems doing so....Fred

 

[Don B]

Fred,

With a groove cut into the plug's face, I'd be concerned about fouling buildup while shooting and difficulty getting the area clean and dry. It would feel like the same problems that would come from not getting a good seating of the breech plug onto the barrel shoulder.

Don

 

[Birddog6]

Unless you are going to rebarrel the rifle & move the barrel back, your choices are limited on what you can do as the barrel & lock are set in place. So....... the vent hole will be where the vent hole will be. If it is AT the edge of the breechplug face, regardless of the type of vent liner you install, you will need to make a groove in the breechplug face to help with the ignition or it is gonna foul after every shot.

No, it is not the way I would or others would want it to end up. But again, you have to deal with what you have to work with.

:thumbsup: