ronlaughlin
The deeper concavity that was introduced seems to help; since making the modification there have been zero ignition problems. However, after firing the rifle so many times the primer seat started to erode, and this flame cutting became worse and worse with use. To fix this issue, i utilized information provided by Busta, and prepared the plug to use o-ring under the primer.
In the beginning I did the same thing - I sank the vent liner inot the plug to reduce the distance the flash needed to travel. Thinking this would really help the ignition of BH. This is a Knight plug that I converted using the Lehigh Vent Liner.
Even Dave @ Lehigh was convinced that reducing the length of the flash channel was the way to go.
After shooting his vent liner and then considering the length of the Triumph plug, which works very well by the way with BH, I wondered how important is it to reduce the length of the flash channel...
IF you are using a Lehigh vent liner. After a lot of consideration I decided the added length of the flas channel was beneficial to reducing the 'felt' blow-back pressure on the primer and as in the Triumph hoping it would also reduce the amount of blow-back gas that might escape.
My reasoning was if the the 'flash Channel' could contain more blow-back volume and allow the bullet to get out of the muzzle - then on exit the gas would then be sucked out of the breech plug. Increasing the volume contained was the key - so by lengthening and drilling the flash channel to a larger diameter - I believe I have accomplished this.
Here is an example.... The Vent liner has been installed on the end of the plug, increasing the length of the 'flash channel' and the channel has been drilled with a #21 bit. Then to test the operation I shot 20 shots through the Knight using the normally really dirty Red Plastic Jacket and these jackets were used one on top of that.
Here is another look at it....
Moving to a NFPJ makes it all the more cleaner... This is a picture of a NFPJ with the vent liner installed on the end of the plug... The white substance you see on the bolt is lithium grease. I put the grease on to catch and trap blow-back material so I could see it better.
This is the operational theory of my conversion attempts...
I really should give creadit where credit is due... and that is the Lehigh Vent liner. The reversed cone effect of the vent liner forces a given amount out and away from the flash hole and into the barrel. The breech plug nor the liner act as a funnel directing the blow-back back up the flash channel.
The other effect of the vent liner... I use a W209 to ignite BH and have not had a problem at all. Actually I even use a cooler Remington 209-4 (410 primer) and Win T7 primer - all work equally well. I have shot 90 grains to 140 grains of BH with these combinations - The chrono shows no really difference in velocities with any of the primers, although the impact points move a little left and right - all provide excellent groups.
Maybe because of the different metals used in the Breech Plug - I have not yet seen any gas cutting on the Knights, Omega, or Remington 700ml plugs... Guess I am just fortunate.