Not long ago JStanley provided a link to a page that animated Bernoulli's Principle. This page got me to thinking about breech plugs and ventliners more than i already had. While thinking on these things, it occurred to me that all available ventliner are designed to be used with smokeless powder. So i began wondering what a ventliner designed for black powder, and BPsubs, would look like. To me, Bernoulli indicates that a smaller flash hole the can transmit as much heat energy as a larger flash hole; within reason of course. This past winter, i learned, with no doubt that a 0.028" flash hole works great igniting BH209. All the available commercial ventliners have larger flash holes, and i believe they were designed for smokeless powder rifles. When one modifies a CVA breech plug, so it will work reliably with BH, a ventliner is a critical component.

A while back Screwbolts suggested i use Holo-Krome screws to make ventliners. My local machine shop and supplier was able to get me a box of them screws; they cost me about 20 cents each, including tax. They are made in USA. They are some hardened, and information provided by Screwbolts indicates they will resist erosion during the explosion of powder and primer.











Today, i was able to drill 10 screws with one #70 cobalt drill, that had been used already to drill flash holes in 5 breech plugs made from grade 8 bolts. I then tossed the $3 drill, and drilled another with a new #70 drill. I never broke a drill, or ruined a screw today.

The ventliner has a tapered end, and then a stepped flash hole. The flash hole goes from the taper to about 0.0469", and then to 0.028". The 0.028" portion of the flash hole is a bit less than 1/8" long.

I am hoping to get hundreds of shots per ventliner, before the flash hole erodes to over 0.033"; time will tell.

I use 100 gr. of T7-FFF with 250 or 300 gr.Quite sure it will last for 500 shots.
Taureau noir