saxman1

My GM barrels have a clean out screw and you can feed a pipe cleaner in that and with a good pen light you can see it come out on the BP. The pocket in the BRP of a GM barrel is a bit larger than that in a TC barrel - infact if i drop my bore light in the barrel to fast it will get stuck in the breech plug.

If I remember right the flame channel comes out on the top of the powder about a 1/3 of the way up on the load. So infact you are igniting the top 3rd of the powder load. You are not starting the burn at the rear of the powder - helps reduce some blow back effect + gives a more efficient burn.