GPR touch holes

[ebiggs1]

As stated in a previous thread, the initial outing with the Lyman GPR was something short of stellar. I had three flash-in-the pans.
Upon observing the touchhole liner I discovered it was less than 1/16 inch.
Since I had three extras, I decided to drill. The top one is with a #50 (.070) drill bit and a small cone.
The middle is just the #50 drill. And on the bottom is a 1/16-inch hole. The only one I tried so far is the 1/16-inch and it shot 10 times out of ten times when I quit for the day.
Plus the flint had the previous ten strikes on it.

 

[silverfox]

Wait until you try the top one. If it doesn't self prime it should stop the flash in the pan. Of course you will still have to do all the other things you have to do to make a flintlock work.
You did cone the back sides It is as important as coneing the front side if not more so. That moves the powder closer to the pan and makes for a faster ignition.
Fox :thumbsup:

 

[stude11]

Keep in mind that the larger hole you have, the more fire and pressure will squirt out of it. I've seen a badly eroded touch hole actually shove the flint diagonally in the jaws. I'd go with the smallest one that gives reliable ignition, and like
silverfox said, cone the backside rather than the front.

 

[ebiggs1]

These are Track's touch hole replacement liners and the back side looks pretty good as is.
Remember the small one is .0625 and the larger ones are .070. That makes only .0075 difference.
My TC came with a nice touch hole liner that was .070 already.
Thanx guys,
EB

 

[Zonie]

Just as a point of interest?, a little change in the diameter makes a lot of difference in the open area of the touch hole.

Going from a .0625 diameter to a .070 changes the open area 25 percent.

 

[ebiggs1]

You brought to my attention a sometimes overlooked fact. Thank you. A small number can make a huge difference. Just because the number is small it is relative to what we are doing.
But I think .0625 to a #50 drill (.070) is closer to a 12% increase. 25% would be closer to 5/64th.
If my aging math is still coherent.

 

[mykeal]

Increasing the diameter of the touch hole from 0.0625" to 0.07" is a 12% increase in diameter but a 25% increase in area.