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.