Touch Hole Size

[Bougalee]

Like the OP, I'm getting to know a new smoothbore. Mine is a Fusil de Chasse from TVM. First got it, many, flashes in the pan, decided to drill out the hole in the liner to 1/64, don't know what the hole was but it was tiny. Bad things happened. To my surprise I lost all velocity and it appeared that the touch hole was now too large and I was losing too much gas. Surprising as I had drilled out a liner in my GPR much larger with no problems with greatly improved function.

Got a new liner and started again. Same old flashes in the pan. Decided to try new powder the one I had been using is ffg, Elephant Brand and was a gift. Don't know the history of the gift. Had some new Graf and Sons ffg and that seemed to improve things quite a bit. Still not as reliable as the GPR with the bigger liner hole. I'd like to hear what you guys think of the situation.

 

[Grandpa Ron]

What powder are you using for primer?

I would think a .062" touch hole would be fine. My touch hole starts about .045" and I replace it when it gets to .090".

 

[Bougalee]

I began using 3f for primer and I'm currently using 4f. Haven't shot it enough yet to tell if there is a difference.

 

[Zonie]

... decided to drill out the hole in the liner to 1/64, don't know what the hole was but it was tiny...

I believe you intended to say 1/16?

1/64 = 0.0156.

Not to sound argumentative but I find it hard to believe a 1/16" touch hold would lose enough gas pressure to be noticable.

I know on my rifles the only difference that can be noticed by enlarging the touch hole without increaseing the powder charge is the point of impact of the group will drop a little. Usually this is no more than 1 inch at 50 yards.

 

[Bougalee]

Your right I did mean to say 1/16. Quite frankly I'm totally confused, I'm at a loss to explain what happened after I drilled out the liner. Guess it's the powder, that's the only thing I can figure at this point. More shooting to follow? So much to figure out. A project for sure, hope I can figure something out before turkey season.

 

[Grandpa Ron]

Just a random thought, where is your touch hole with respect to the breach plug?

I once built a rifle and ended up drilling the vent so close, the drill laid across the breach plug face. I did not take long to fill with fouling.

I ended up skiving the plug face to allow more room for powder.

Thing do not always go as planned.

 

[Bougalee]

Ron it appears to me that there is ample room from the breach plug. I've been making sure to pick the vent which has seemed to remedy the ignition problems. I don't have to do that with my GPR and sometimes forget to with this fusil which seems to me to be a bit more fussy. It's a learning process all the way around.