I posted this on another forum about building my flint lock.

As for the touch hole. This is what I thought to do.
Drill a hole and test fire the lock. The hole, if WITH A LITTLE LUCK correct will be enlarged to have a stainless liner.
Also need clearance for ease of pick tool access. Have a low speed drill press, cutting oil the drill and tap the size needed for the liner.

I was told this to my surprise.

Forgo using a stainless steel touch hole liner. Old guns had no liners.

And some old guns had platinum liners. But you can't just drill a hole; it will be a long, thin channel to the powder and you will have very slow fire time; it needs to be enlarged so that the main charge is looking at the pan. Some cone the outside of the barrel, but a liner with a cone or radius inside is better. Put the touch hole at the TOP of the pan, not the bottom; you want the pan powder to flash across to the hole, not burn down until it gets to it.

I have used both. For a more traditional look,,just use a drilled hole and keep the liner for when the hole enlarges to being useless ,,like in 30 years if you shoot alot.

Unless you have a very small bore in a very large dia bbl, the speed at which it fires will not be objectionable in most cases.

Keep the flash hole clear of powder, both main charge and pan/primer so as not to create a fuse burn effect. You want the flame from the pan to flash ignite the charge in the bbl,,not burn it's way to it.

Before loading the bbl charge, many used to plug the flash hole with a quill or other slender pick and then remove it after the rifle was loaded. That left the flash hole clear.

Use a minimum of primer powder in the pan. Excess is just that and doesn't make the rifle fire any faster. It doesn't take much at all to fire if all is working well.

Some originals and a few custom made guns were/are externally coned in the flash hole to allow a larger entrance for the flame.

Originals were sometimes coned from the inside. A couple of different ways and tools to do it. The simplest and crudest I saw was to drill the flash hole right on through the bbl and out the left bbl flat. Then the hole from the left flat enlarged to allow access to the flash hole from the inside where it was coned with a shaped bit. Then the extra hole in the left flat/wall was plugged back up with a screw and rivited over.
Some T/C percussion breech plugs are made that way and they leave a small allen screw in the left wall for cleaning access I guess.

The general opinion is to place the flash hole at the top 'sunset' position in the pan. But recent tests and high speed photos have shown no difference in firing speed to one placed low in the pan.
A little easier to clean out with your pick if it's up higher though.
Plus if you ever go to sell it,,a low in the pan flash hole will be a turn off to most shooters as they cling to the 'high in the pan' idea.

Little if any difference in using 4F for priming or a pinch of your main charge powder. Some even think it's a little faster with the 3F and 2F powders. I've used them all and they seem about equal to me in efficiency.

With all that said,,,a flash hole liner will work as advertised if you do use one. I put one in my 50 F/L and it fires very reliably. But it fired just as reliably before that w/o one and to my ear, just as fast.
I installed one after a dead charge afield left me rifleless. Ball puller didn't work either.
They're nice if only for that reason that you can remove and trickle a bit of powder in behind a bad or even a dry load and then re-install, fire, and you're back in business.
But I've never had to do that again!

My 31 cal F/L never had one and it shot just fine that way.
You can always install one later if you wish. The flash hole is on the same center.

Thanks dpcd and 2152hg,
This is a Green Mountain 42" x 1" ATF barrel in .50 cal. Chambers Large Syler lock and Davis set triggers. OAL 60"

Dry fire lock time is a little slow. How to step up the lock time?