What is a touch hole liner and what does it do?
A touch hole liner is a threaded bushing installed in a drilled and tapped hole in the barrel where the pan powder flash ignites the main charge. It is counterbored on the inside to form a cone that brings the powder charge closer to the outside of the barrel, and it shortens the flash channel, which helps the rifle fire a bit faster and stay cleaner since the shorter channel fouls less.