How Does a Touch Hole Liner Improve Reliability?

[Newbert]

As per an earlier thread I'm in the process of "back loading" my rifle with a dry ball and in doing so I removed the touch hole liner.

I am curious what exactly this piece does. All my searching says it makes firing and igniting your primary charge more reliable, but I dont understand how.

The liner seems to be a threaded insert that makes the touch hole about 60% more narrow.

If anything, by narrowing the hole wouldn't it only make it harder for an ember from the pan to actually reach the powder? Clearly the people who invented this piece and the people still using them aren't fools so it's me who is ignorant but could someone explain this?

Thank you for your time! I appreciate everyone's responses. They are very helpful

 

[snakebit]

I cant really say, an engineer probably could, but I replaced the one on my GPR, and now have 100% reliability. The new RMC OX-YOKE one I put in is hour glass shaped. I am guessing it disperses the heat better? Definitely kept me from sucking my rifle in the creek.

 

[yellowhammer]

As per an earlier thread I'm in the process of "back loading" my rifle with a dry ball and in doing so I removed the touch hole liner. I am curious what exactly this piece does...

Articles to read:
Touch hole liner vs straight hole
Flints, Fizzens and Touch Hole Liners

 

[Grenadier1758]

Most touch hole liners are internally coned or drilled larger than the touch hole leaving a short passage for the heat to go through the touch hole.

 

[RobertIN]

We're not necessarily relying on a spark or ember going through the touchhole, as much as we're relying on the flash of heat (BP has a very low flashpoint). As others have mentioned, a coned or flared internal section of the touch hole provides a wider section with more powder right behind the hole to accelerate ignition.

 

[Larry (Omaha)]

As per an earlier thread I'm in the process of "back loading" my rifle with a dry ball and in doing so I removed the touch hole liner.

I am curious what exactly this piece does. All my searching says it makes firing and igniting your primary charge more reliable, but I dont understand how.

The liner seems to be a threaded insert that makes the touch hole about 60% more narrow.

If anything, by narrowing the hole wouldn't it only make it harder for an ember from the pan to actually reach the powder? Clearly the people who invented this piece and the people still using them aren't fools so it's me who is ignorant but could someone explain this?

Thank you for your time! I appreciate everyone's responses. They are very helpful

You are incorrect about narrower. Yes narrower from the widened funnel diameter on a TH liner, but not more narrow then the basic 1/16" diameter that usually works the best. That 1/16" is the TH flash hole dimension.
The liner's purpose shortens the flash path to the powder, which of course shortens ignition time. A SS liner also provides longer life to a TH that is just a hole in the barrel.
Larry

 

[Cruzatte]

If anything, by narrowing the hole wouldn't it only make it harder for an ember from the pan to actually reach the powder? Clearly the people who invented this piece and the people still using them aren't fools so it's me who is ignorant but could someone explain this?

Thank you for your time! I appreciate everyone's responses. They are very helpful

It isn't an ember from the flash pan that ignites the main charge. It is the heat of the flame that does that job. The touch hole liner is coned on the inside. This moves the powder in the bore a little closer to the heat source when the priming charge ignites.

 

[hanshi]

A liner of stainless steel or other tough metals will last longer than the tiny hole through the barrel steel.

 

[Spikebuck]

I have a rifle without a touch hole liner. It is reliable, but not quite as much as my other rifles with liners. It is also just a tad slower ignition time. It all works fine, but I have to be a little more careful in my loading regimen and I always pick the touch hole to ensure a clear channel where I don't have to do that with liners.

 

[ekettenburg]

In terms of speed of ignition and increased reliability, the liner itself is not doing anything. The fact that the liner is internally coned and allowing the pan charge to be closer to the main powder charge is what is changing the equation. Most people do not have the proper tools or ability to internally cone the barrel itself, so it is easier to buy or make an internally coned liner and simply drill and tap it into the barrel. Also, as noted above, the materials of which most liners are typically made have a higher resistance to corrosion and burnout than soft iron or 12L (most modern barrels), which is another more modern consideration.

Historically liners were very uncommon on American arms and much more common on higher quality European civilian arms. Most were made of gold or platinum for the corrosion resistance and burn resistance.

Straight drilled vents tend to be of larger size than the common (today) 1/16" or less to accommodate the increased distance from pan to main charge. And they need to be picked religiously.

 

[James Kibler]

Larry Pletcher's testing found that a liner increased ignition speed a small amount (around 10% I believe) for clean unfouled barrels and liners. The main difference noted was how much cleaner the coned liner stayed as opposed to a long parallel sided hole. His conclusion was this is the main advantage.

 

[Rob M.]

As stated before ....the liner is a large cone on the inside so the main charge , the powder at the breech, is much closer to the pan ... I like to make a cone on the inside of my touch hole , round ball bit on Moto tool , and I drill my touch hole a little bigger than most , 5/64 , and then I drill , ( JUST a bit ! ) from the outside , a .092 ....just to cone the outside of the T.H. I like it . With that set up and the proper placement of the T.H. in relation to the pan , centered , level with top of pan , the ignition is VERY fast ! ....

 

[M. De Land]

As stated before ....the liner is a large cone on the inside so the main charge , the powder at the breech, is much closer to the pan ... I like to make a cone on the inside of my touch hole , round ball bit on Moto tool , and I drill my touch hole a little bigger than most , 5/64 , and then I drill , ( JUST a bit ! ) from the outside , a .092 ....just to cone the outside of the T.H. I like it . With that set up and the proper placement of the T.H. in relation to the pan , centered , level with top of pan , the ignition is VERY fast ! ....

I make my own liners of tool steel and much prefer to cone the exterior rather than the interior thus achieving the same dynamic and discouraging exit flash/pressure with the interior coning. This design vectors the flash from the pan inward rather then the pressure from the main charge ignition outward.

I have never cared for White lightning liners with the interior coning as they vector a lot of main charge pressure outward unnecessarily. The same dynamic of shortening flash hole length can be achieved in reverse with better main charge pressure containment.

 

[tenngun]

I built a NWG from Track of the wolf. In keeping with the way they were sold I drilled a straight touch hole but was unsatisfied with the ignition
I’ve shot flinters since 1977 and don’t notice a delay, but on this I noticed a delay right away.
I shoot ten to fifteen shots in an outing, and maybe shot a hundred rounds through it.
Just never got used to the slow ignition
Replaced it with a white lining and it shot like a dream
My time is more eighteenth century and the gun didn’t fit, so I sold it for cost.
All my flinters have a liner except one, a 76 cal musket with a straight touch hole. And in that I don’t notice a delay