I am including parts of two articles from muzzle blasts just for information.
Bob
Muzzle Blasts Online
February/March 1999 Volume 4, Number 1
Flints, Frizzens and Touch Hole Liners
by Charlie Maggard
When I make a liner, I want a funnel-shaped interior (see the drawing) and not a tube. Think about it: stuff will go into a funnel easier than into a tube. After I drill the diameter hole that I want, I use a cone or "Christmas tree" shaped carbide cutter to shape the internal part of the liner to a funnel shape. After the liner is installed in the barrel, I put a shallow cup in the outside face of the liner with a ball type carbide cutter. With this type of liner I can usually see powder grains in the touch hole after loading the rifle. I don't "pick" the hole before shooting, and flashes in the pan are very rare. The internal shape of the liner appears to create a self cleaning action. The ignition is super fast, and I have not had a liner blow out.
The hole in a percussion nipple runs between .020 and .030 in diameter, depending upon the manufacturer. This size hole is not practical for good ignition in a flintlock. For best results I use a liner with a .062 (1/16th.) hole for my flintlocks in .40 caliber or larger. For .32, .36, and .38 calibers, I like to use a .050 hole in the liner. With the smaller powder charges that are normally used in these small calibers, the .062 hole allows too much jetting of main powder charge out of the touch hole. This causes erratic pressures and affects the accuracy. The lag time between the jetting and ignition of the main charge makes it more difficult to hold through on the target in the offhand position, especially with a flintlock pistol. The smaller hole reduces the pressure loss from the main charge in a smaller caliber. I replace the touch hole liner when the hole gets about .008 larger than the original hole size, or when the accuracy falls off. A good, properly shaped liner should last for about 800 to 1000 shots, and that is a lot of shooting.
The best hole gauge and vent pick that I have found is a set of welding torch tip cleaning wires. These can be bought at any welding supply shop. To check the size of the hole, insert the largest wire that will fit into the hole, and then measure the wire with a dial caliper or micrometer. If the hole is too large, then replace the liner.
Stainless steel and a copper beryllium alloy are the best and most common metals used for touch hole liners today. Even these metals will eventually erode and the hole will enlarge. The pressure of the main charge jetting out the hole is similar to a oxygen acetylene cutting torch in heat and erosion. The larger the volume of the main powder charge, the faster the liner or nipple will "burn" out. In the early days, liners were not used in flintlocks in America. There was only a hole drilled into the soft iron barrel. The soft iron eroded from heat and pressure very fast and really slowed down the ignition. This is where the old FZZZZZZZZZZZ BOOM!! came into being.
In later American and European guns, before alloys and stainless steel, touch holes and nipples were lined with gold or platinum. Even though these metals are soft, they have a very high melting point and are very erosion resistant. No one makes gold or platinum lined nipples or vent liners anymore. These are an unnecessary luxury today.
Muzzle Blasts Online
August/September 1999 Volume 4, Number 4
The Flintlock Revisited
by John Woolfolk
One problem can be the humidity. A rifle that works well in a dry climate may become fussy where it is humid. After you fire, watch the fouling in your pan. Does it start out gray and quickly turn to a shiny obsidian-colored puddle? Under such a condition, a 1/32" flash-hole is just asking for problems. In damp or humid climes, I consider a 1/16" touch-hole to be the minimum. Plus, if you dump your priming into such a mass of shiny, damp goo, it will absorb moisture, and after a short time, it will not burn as rapidly as it should, if it flashes at all. [Editor's note: Under such conditions, you might try priming with FFFg or even FFg; since those granules are larger and graphite-coated, they are less susceptible to minor humidity, and they still flash reliably and quickly.]
Well now, let us suppose that your powder always flashes but you don't always get ignition, even with a full-sized touch hole. It might be the placement of your vent that is the problem. The vent (touch hole, flash hole) should be just about level with the top of the pan. (Or a bit lower if you have one of those locks with a pan that holds about a pint of powder!) If your vent is a bit high, opening your touch hole to 5/64th may take care of the problem, but a better solution is to remove the vent liner and replace it with a liner that has the vent off-center, so that it lines up with the top of the pan. My favorite flinter was converted from percussion to flint, forcing this solution to be used. The vent liner is made from a hardened stainless bolt. It has lasted for thousands of shots. A wire gauge still shows no discernible wear, and my chronograph still reports very little deviation in velocity from shot to shot. (Oh I know, the super-competitive shooters change liners about as often as they do their socks. I'm not arguing with them. I just go by the old axiom, "If it ain't broke, don't fix it!")
Often times, the vent-liner itself is the villain. The old-timey rifles simply had a hole bored through the barrel to the powder chamber. How those guys shot well with that arrangement is a mystery. That long touch hole would act as a fuse and slow the ignition terribly. A properly made liner has a hole of about 1/16" to 5/64" in diameter that is only about 1/32 to no more than 1/16th of an inch in depth. Inside of that, the liner cones out to almost the full diameter of the insert. This puts the powder right by the priming charge. Ignition is quick. Some vent liners have touch holes that are a quarter-inch long, or more, before they enter the cone. Not good! Check your vent liner. Most on the market are fine. Some are little more than a bad joke!
