What size flash hole?

[GM54-120]

Toby's breach plug page is what a few of use were trying or wanting to try. I think he is about right but the guys on this forum took it to the next step with the lehigh vent liners.

IMO the domed shape of the vent liner should work great with all powders and probably all primers.

I emailed him a while ago about adding the Lehigh vent liner and didnt get a response but he may be busy atm. He mentions a tapered transition from channel to the hole but isnt sure if or what plugs are shaped this way.

The liner insures you have this smoother transition and the domed shape should help with blowby too. The one on his page may ignite VERY well but i had my concerns about too much bowby with the huge recess.

When i get a chrono i want to test my modified BP with JSG using the standard Lehigh liner and a short stemmed liner just to see if it helps velocity and fps variations.

 

[sabotloader]

tpcollins

In your case the length of the Triumph BP has the same properties as creating a larger diameter flash channel... so that part of this problem has already been done for you. In fact after looking at my Triumph plug and thinking about "why is this plug so darn clean?" - that is what started me on this quest to create a cleaner plug in every thing I own.

I know Lee has modified one of his Triumph plugs with a Lehigh Vent Liner, but I am not sure if he drilled the entire channel to a #21 bit. It probably would not be necessary. It already has the ability to hold additional volume.

That additional length is also what makes the Triumph plug work well with BH even though it has a smallish diameter 'flash hole'. But in the case of the Triumph I would think you would need to use the hot primers like Fed-209a or the CCI-209m.