Treso touch hole liners are made from the same tough and erosion resistant Ampco alloy as the Treso nipples. Flash hole is .0625 diameter. The Treso flint touch hole liner is installed in a 1/4×28 thread in the side of the barrel with a screwdriver (see information below for specific instructions on installation). This model is removable with a screwdriver and is handy for interchangeable flint/percussion lock firearms. We recommend anti-seize material be coated on nipple and touch hole liner threads to make them more easily removable.
Installation Instructions — Screwdriver Model: For firearms with interchangeable flint/percussion locks, use 5/16×24 thread and matching percussion drum (install drum and percussion lock first for proper location). Use 1/4×28 thread size for touch hole only replacement applications. Drill and tap breech with appropriate thread and slightly chamfer threaded hole with 82 degree countersink. Install touch hole liner with screwdriver. Touch hole liner should be flush with outside of barrel; if not, adjust chamfer. Check for clearance inside of bore and shorten touch hole liner if necessary.