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Optimum flash hole distance from breech face?

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Sidney Smith

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What do you consider the optimum distance for the flashole to be in relation to the breech face. I just drilled, tapped, and installed this flash hole liner tonight in my .75 caliber matchlock barrel. It's coming in right around 5/32nds, or .16 inch from breech face to the center of the flash hole. I always allow for a radius distance plus a hair from the edge of the liner to the breech face so I'm not drilling into the plug, which puts the flash hole where it is. I guess I could drill the hole slightly closer since the liner isn't going all the way into the bore, but I don't like the idea of hitting the breech face with the drill. What do you think?
20220327_200317.jpg
 
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I use the 1/4 x 28 tpi stainless touch hole liners ,and install them with the touch hole even with the breech face. When the drill touches the breech face , stop drilling. the drill bit deflect from the breech plug face, will elongate and ruin the untapped touch hole . Grind and or file off the excess liner. I prefer a 1/16 " touch hole so drill out the hole. Hope this is clear.
 
What do you consider the optimum distance for the flashole to be in relation to the breech face. I just drilled, tapped, and installed this flash hole liner tonight in my .75 caliber matchlock barrel. It's coming in right around 5/32nds, or .16 inch from breech face to the center of the flash hole. I always allow for a radius distance plus a hair from the edge of the liner to the breech face so I'm not drilling into the plug, which puts the flash hole where it is. I guess I could drill the hole slightly closer since the liner isn't going all the way into the bore, but I don't like the idea of hitting the breech face with the drill. What do you think?
When one has a liner as you do, I think what you show is perfect. If no liner, then go right next to the breech face with the TH. You don't like the idea of hitting the breech face with a drill and I agree with that. Pulling a breech plug to me is no biggie, so if I wanted to move the liner closer I would remove the breech plug first. I still like to put my liners in just like you did.
Larry
 
The way you did it is the way most would prefer. Some people like to notch the breech plug. I personally se no advantage to that and significant disadvantages. Either way works.
 
I use the 1/4 x 28 tpi stainless touch hole liners ,and install them with the touch hole even with the breech face. When the drill touches the breech face , stop drilling. the drill bit deflect from the breech plug face, will elongate and ruin the untapped touch hole . Grind and or file off the excess liner. I prefer a 1/16 " touch hole so drill out the hole. Hope this is clear.
I'm using the same type of liners. I prefer the kind with the wrench lug that you then hack saw away to reveal the touch hole. I drilled the hole to 1/16th and also slightly countersunk the outside as you see in the photo. The countersink helps with ignition, and also aids in removal via an easy out, should the liner ever wear out.
 
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I have never intentionally notched a breech face. I see no need ,or advantage of doing it. I've restored a few original longrifles with notched plugs , and several original European muskets with notched plugs. I can understand ,on an American longrifle seeing the occasional notched plug , perhaps due to errant pan placement ,but have no access to foreign gun production records , to know why some of those guns , had notched plugs.
 
I cant remember if it was Col. Hawker did trials, or it it was in AnEssay OnShooting, (1789) or some such date, but they conducted trials on how hard a gun shot. (no measure for velocity as such back then)
It seems that it does not make a great deal of difference how far from the breech face the touchhole is, I believe they went way forward, well over half an inch!
The outcome was, keep the touchhole forward of the breech face a little , as right At the breech face caused more stoppages with fouling than a touchhole further forward.
Now I will have o go look for that trial!
 
I cant remember if it was Col. Hawker did trials, or it it was in AnEssay OnShooting, (1789) or some such date, but they conducted trials on how hard a gun shot. (no measure for velocity as such back then)
It seems that it does not make a great deal of difference how far from the breech face the touchhole is, I believe they went way forward, well over half an inch!
The outcome was, keep the touchhole forward of the breech face a little , as right At the breech face caused more stoppages with fouling than a touchhole further forward.
Now I will have o go look for that trial!
Makes sense, as when swabbing between shots some fouling is going to be pushed toward the breech plug.
 
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I do on occasion find the need to notch a breech plug face, I use White Lightning tough hole liners, polish the face and notch, I don't swab at all, I cannot remember the last time I had to use a vent pick, I think on a .40 without a notch, other than refreshing the flint edge, I don't have any miss or hang fires.
Robby
 
What you did is perfect. If it got any closer the barrel wall ahead of the breech plug would be severely weakened from the threading of the liner.

I personally think you should leave 1/16" or so anyway which would leave some room for fouling to build up. Unless you are planning on shooting ultra minimum loads (like with he ball just touching the breech face) having the fire reach the powder column part way up it is of minimal impact on pressures and velocities.
 

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