The length of the flame channel in the plug is the same as the OEM plug. In the plug that utilizes the o-ring the one end of the flame channel is rubber i.e. the perimeter of the flame channel for about 0.75mm is the compressed o-ring. The flash hole at the end of the breech plug can't be much larger than 0.034" because that would allow granules of powder into the flame channel.

The hole in the end of the adapter is similar to the hole in the end of the shotgun primers. If one wants to say there is two flash holes when using rifle primers, then one could say there is two flash holes when using shotgun primers. The flash hole in W209 primers is about 0.092". The flash hole in the end of 209A primers is about 0.102" The flash hole in the PR Bullet primer adapters is about 0.082".