Flash Hole location

[Reegee/Flint]

I know this information is here somewhere But how far ahead of the breech plug should the Flash Hole be drilled? This is a Rice bbl and the plug appears to be flat, not tapered or coned.

[flehto]

Mine are always located so that there's 1/32" from the edge of the liner to the plug face. If it's  just a TH, then it's 1/32"-1/16" from the TH edge to the plug face. Vertically I try to put the centerline of the TH at the top level of the pan or slightly below. This has worked well for me. but in hunting situations, who knows where the powder charge is.....Fred

[rick/pa]

I believe this post might have the information you're seeking.

https://americanlongrifles.org/forum/index.php?topic=13907.msg131325;topicseen#msg131325

[WadePatton]

We try to miss the plug-barely.  When we don't miss the plug, the plug usually gets a notch or groove cut into it to allow the primer flash to ignite the load.   

The risk in getting it too far forward is when a dryball gets seated at (blocking) or behind the vent such that ball pulling in that situation offers less options (no way to shoot it out with trickled in powder, nor to push it out with grease).

[Scota4570]

I put liner as close to the plug as I can.  With a 1/4" liner I would spot my center 1/8" plus about 0.030" in front of the plug face.  I would never notch a plug.  IF I botched it and put the liner to far back I'd cut it all off and start again.  Some guys are ok with  a notch plug, you have to decide for yourself. 

The Hugh Tonges scheme of putting the liner in the middle of the 1/2" plug threads gives me the willies.  That idea was linked above.  I may try it soon but with a 3/4" or longer,  length of plug threads.  This is a machine shop operation to do cleanly, IMHO. 

I would not make a gun that did not have a liner. 

[B.Habermehl]

I try to have a quarter inch diameter liner located 5/32 on center from the breech face, or a bit less. Usually with the centerline of the touch hole being about 1/64 of a inch below the top of the locks pan. I don’t get upset if it works out to be a bit closer. I prefer not to notch the breech face, but have in the past with no problems. We bring a modern engineering mind set to building these firearms. The original makers did not sweat notched breech plugs. I’ve seen lots. Maybe not best practices, but they do work. The big thing is having a good breech plug fit to begin with. With out over tourqueing the plug threads. BJH

[Reegee/Flint]

  Thank all of you for your advice and operational know how. I know just what to do now.
As to the vertical alignment I have read all the studies and references , everyone has something different for a fast lock time, low, high, sun set, sun rise? I`ll have to make up my mind when I want to fire it.  If I don`t think it`s fast enough I`ll get it Heli-Arced shut and try another position.
Your thoughts, prayers and ideas welcomed.....

[oldhunter1954]

Being a new builder i will assume you guys use a ram rod to locate where the face of the breech plug is on the barrel.

[WadePatton]

Being a new builder i will assume you guys use a ram rod to locate where the face of the breech plug is on the barrel.

Or it's the distance from the plug shoulder to the plug face. Builders generally have the plug out a few times in the process.

[oldhunter1954]

Being a new builder i will assume you guys use a ram rod to locate where the face of the breech plug is on the barrel.

Or it's the distance from the plug shoulder to the plug face. Builders generally have the plug out a few times in the process.

Interesting, I thought the golden rule was to never remove the breech plug from the barrel?

[Eric Krewson]

Except for Rice barrels and perhaps some that I haven't used you will probably find a poor plug to breech face fit that will need to be adjusted.

As far as removing a breechplug, a no no on most CVA type rifles but a common practice on every other barrel for a variety of reasons during the build and for loading boo boos that the leave you no other option to get the offending article out of the barrel.

I once put several thin over shot wads down my fowlers bore first(daydreaming), no way to get them out with out removing the breechplug. Once I thought dryballed and couldn't get my ball puller to grab the ball, I pulled the breechplug to find an empty bore, DUH !

[Ken G]

I normally remove one at least twice.  To check the plug fit and to mark plug face for placement of the vent liner.  I also remove it when installing the vent liner and to make sure the vent liner doesn't protrude into the bore and create a snag for a jag. 

Ken

[Scota4570]

To determine where the plug stops, I measure the plug and transfer the measurement to the barrel.

I use digital calipers.  I could not do anything in the shop with out them.  If you don't have one buy one.   

Vertical position?  Center of the flat.  Lock position?  top edge of the pan, center of the flat. 

The liner will need to be trimmed inside.  I cut a piece of brass sheet.  I put a liner sized hole in the sheet.  I then roll the brass to fit inside the bore.  I then grind the liner, very carefully, with a ball shaped stone on a Dremil.  I make it flush with the bore.  IF you don't use the brass when you slip you will mess up the bore. 

[Scota4570]

"but I’m somewhat tempted to eschew the liner for tradition’s sake."

IF you do not use a liner it will be less reliable, ignition time will be longer,  you will be constantly fiddling with it to make it go off.

As long as the drilled touch hole is properly located you can add a liner later when you get tired of fussing with it.     

[heinz]

Scota, there were rifles built with touch hole liners, there were rifles that had liners added after the touchhole got too large (burned out)  I used a 3/32 touch hole in hunting and rendezvous gun.  Very fast but you can get some vertical stringing.  It is best  to keep the vent plugged when you load with anything bigger than 1/16