Breechplug
I asked you a question about the BP and the concave end VS the Flat end and the pourpose of them, when you get a chance can you answer it on the forum?
BP I can only give you what I think I thought.... I have always thought the the flat face BP was designed for pellets - especially for Pyro pellets with the black powder accelerator on one end. And then when T7 pellets came along - I made the assumption the flat face continued to give the flash a direct path up the hole in the pellet to begin powder ignition.
The concave faced breech plug seemed like a natural for the ignition of loose powder. I offered the ability of the flash to ignite the bottom of the load -start the hot ignition and then spread. I also have to tell you that I shoot a version 2 of Doc White's 209 breech plug in my model 97. It does have a flat face and is excellent for the ignition of loose T7 as well as Pryo Pellets.
The faces of the breech plugs went through many changes with the advent of T7 and
Underclocked's famous invention of the 'Crud Ring". There was an industry wide effort to change the face of the BP to help reduce the 'crud ring' build up. From that effort you can see many different designs and depth of the concave faces.
I think the next thing to follow was the 'Convex' faced BP again designed for loose powder. I think the driving force of the 'Convex' face was an effort to clean up the amount of blow back that was sent back up the 'flash hole'. The 'Convex' face would cause some of the blow back pressure to be moved away from the 'flash hole' and conversly the 'Concave" face directed the pressure into the flash hole.
The next thing that has been fooled with is the size of the 'flash hole'. I think the low end of this is .027 used by Knight to reduce blow back and to a high of .036 created by Busta to get better ignition of BH.
Just my take.... and I am not an authority...