Touch hole umph

Put a .45 7/8 on a SMR. Back in the day most guns just had a straight vent for a touch hole. I have had such on a few guns that worked well.
But first time out with a 1/16 touch hole, right in sunset position I had poor ignition.
I waffled for a time thinking about coning out side, but sent off for a white lightning.
Just when you think your finished up pops a project.... oh da horror da horror

1/16" is too small. 5/64" will work MUCH better.

I bought a special cherry that cones the barrel on the inside from somewhere. Can't remember but it works great and I get good ignition.

If one wants to shorten the flash hole length why not cone the exterior of the port rather than the interior?

I got a WL vent liner with this SMR kit and the vent in it doesn't look anywhere near .0625.

Good vent liners can be made from stainless 5/16" allen set screws with a 5/64" hole drilled through.
The set screw socket makes for a good entry hole for the priming flash.
I know stainless allen set screws are not period, but then again standard flat stainless liners are not period either.
Platinum ones are!
Loctite will hold it in place just fine.
Fred

M. De Land said:

I got a WL vent liner with this SMR kit and the vent in it doesn't look anywhere near .0625.

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Liner holes are made undersized to allow drilling to the desired size.

M. De Land said:

If one wants to shorten the flash hole length why not cone the exterior of the port rather than the interior?

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I thought about that, then decided on a liner

Stophel said:

1/16" is too small. 5/64" will work MUCH better.

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I thought about that too, but I have never went bigger then 1/16, but never had this thick of a wall tween charge and flash.

tenngun said:

I thought about that too, but I have never went bigger then 1/16, but never had this thick of a wall tween charge and flash.

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If the wall is that thick, an internally coned liner would help a great deal. Just get the proper drill bit and tap for the thread on the liner you select.
The last ones I have used are the RMC hex tool liners. They look good and are easy to get in and out as opposed to the ones with a flat blade slot on them.
You can get matched bit and tap on Amazon for decent costs if you don't have complete sets of tools for the job.
I set mine up on a drill press table to keep it straight and consistent but there is no reason that you could not do it with a hand drill if you have a good eye and a steady hand.

Yeah I sent for a white lightning from track I have the pilot drill bit and tap for it.

The coned liner will help a lot. A set of Numbered drills will allow you to gradually open the touch hole up. I sort of like the #50 drill (0.070") for the touch hole with a very slight chamfer on the entry.

F.G. Ford said:

Good vent liners can be made from stainless 5/16" allen set screws with a 5/64" hole drilled through.
The set screw socket makes for a good entry hole for the priming flash.
I know stainless allen set screws are not period, but then again standard flat stainless liners are not period either.
Platinum ones are!
Loctite will hold it in place just fine.
Fred

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And usually the set screws are hardened as well which helps in erosion resistance. It seems to me to be a very efficient and practical idea. Never notice it most of the time any way as the frizzen is usually closed.
I do feel the interior of the liner ,no matter which is used, should be contoured to match the bore arch/orbit to eliminate fouling traps or bore intrusion.
The one I made and installed using A-2 tool steel left annealed has no way of removing but to drill out the flash hole and use an easy-out. This is why I left it annealed but wanted to try my idea of potentially coning the exterior rather than interior if it does not fire reliably as is.

M. De Land said:

If one wants to shorten the flash hole length why not cone the exterior of the port rather than the interior?

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Because doing so will often open the touch hole up beyond the area covered by the frizzen. Some people do, and if it is still covered by the frizzen, I suppose it's ok. I have never tried doing it, but never really felt the need to.

Years ago, I started drilling holes at 1/16" (which is just too small for most anything), firing the gun to see what it would do, and then drilling the hole out a little at a time until I got good ignition. (By the way, with a too small hole, I NEVER got the "fuze effect", or slow fire or anything. It would just not go off all the time.) I always ended up at, or very near, 5/64". So now I just drill them that size and that's it. I also cone the inside of the hole with a finishing nail coning tool, though honestly, I have never been able to tell a difference with, or without.

The White Lightning liners and others may have a 1/16" hole, but they have an enormous internal cone, leaving a very thin "barrel wall" for fire to have to pass through.

As per the above, I suppose it would work in theory, IF you got the tip of the cone just right as it entered the bore and the powder chamber. I've not seen it done on historical rifles, though that's not to say it was NEVER done.

When you pick a vent on an inside-coned vent liner, (the kind most builders today use) often you wiggle the pick around to loosen any crud inside the VL and make for a better fire channel. With the cone on the outside, unless the tip of the cone were located perfectly (and what if the hole lands on the junction between a land and a groove?) it would be harder for the pick to clear anything of a cone (with wiggling it around) in to the powder charge beyond the tube of the vent hole.

Also, an outside cone would not very readily allow for a replacement should it become necessary.

In the end, though it may seem more complicated and harder at first, the inside-coned vent liners give you a LOT more room for a margin for error.

I'm thinking what Stophel mentioned is probably the main reason the ODG's didn't cone the exterior, exposing more vent area to the weather, above the top of the frizzen. Now the frizzen in no way seals the vent hole any way but a cone would tend to funnel moisture into the vent hole just as it would flash from the pan.
I am curious about if the idea is practical or not. Wouldn't take any more of a cone than is on a WL interior.
Actually when one looks at a WL it is not really a cone but more of a round bottom counter sink with parallel sides. I just checked mine and the diameter of the cone is about .180. So if your vent is in the sunset position , mid pan, then top of the cone would be .090 above vent center. I doubt you would even notice it with the frizzen closed and if it works good who cares!
Actually I will make mine only about double the size of the .0625 vent hole which would make it .125 in diameter and radius the bottom. It will be interesting to see how this vent works out and how long it will last. May work fine just as it is now with the way the interior is profiled to match the bore wall.

I don't do vent liners anymore, but when I had to, I would drill the hole and tap the threads, and with a bottoming tap, stop the thread short of breaking through to the bore. Fit the vent liner down to bottom out in the threads at the same time the outer "head" bottoms out, and you get everything fitted about as smoothly as possible, with no exposed threads, and with nothing sticking into the bore to have to cut off and dress down.

Stophel said:

I don't do vent liners anymore, but when I had to, I would drill the hole and tap the threads, and with a bottoming tap, stop the thread short of breaking through to the bore. Fit the vent liner down to bottom out in the threads at the same time the outer "head" bottoms out, and you get everything fitted about as smoothly as possible, with no exposed threads, and with nothing sticking into the bore to have to cut off and dress down.

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That's a very good idea! A bottoming tap would be a good tool for the finish. I made an exterior tapered shoulder on my vent similar to the WL that doubles as the depth collar and seal. Once it was indexed I remove and file /sanded the profile of the bore orbit on the interior of the vent, installed and struck of the exterior flush with the side flat of the barrel. No exposed threads in the barrel wall are left to hook fouling. I removed the breech plug to do all this so I could insure a flush fit to the bore orbit. I also decided to leave the rifling in to the breech face in case I dry ball so I could use a ball screw to retrieve it.

Well I had bought a white lightning. Put it in but due to work schedule this was first time to use it. Put 5/64 hole and it shot like a dream. I had two ‘clachtes’ today, otherwise ignition was very fast.