Ron,

When using Knight Bolt Action Muzzleloaders such as the Extreme or Elite, you are fighting another problem which is primer protrusion into the .180" diameter firing pin hole in the bolt face once the primer is sealed tight to the breechplug. Opening up the flame channel to .156" or even a little larger reduces the amount of pressure that the primer sees as it takes longer for this larger volume in the breechplug to pressurize. When the primers protrudes in these guns the are difficult to remove, removal of the bolt worst case, and leak around the primer cup smudgeing up the bolt face (smaller issue). I have used the .125" flame channel with a proper headspaced primer and have had no issues with ignition in these guns. I has only tested mine to single digit temperatures and not below zero. All my breechplug modifying experience is with Knight Extremes and Elites. I believe what you are doing is the right thing for you guns. This is not an exact science yet.

Jim