Determining Vent Hole Position

[Rasch Chronicles]

Fellows,

I had an exhausting day yesterday. Hundreds of cubic yards of moondust into an endless maze of HESCO barriers has a tendancy to do that to you.

I've been following Mr Okies ChunkGun build, and as I finally laid my heavy head down, and felt my weary eyes close, an unbidden thought popped into my leaden mind:

How do you know where to put the vent hole? When I get around to building a flint rifle from scratch, where does the venthole go. Mr Okie's tutorial leads me to believe that it can go anywhere within a limited range, but I would like a little more explaination on the subject if y'all don't mind!

That and I really need to get some sleep...

Best Regards,
Albert A Rasch
Albert Rasch In Afghanistan™

[smylee grouch]

Rest well Albert, when the time comes you can put the vent right at the breech face so cone is right on the breech face edge.    Gary

[Ky-Flinter]

And vertically, the hole should be centered on the top flat of the pan.  Looks like a sunset on the horizon.

-Ron

[Dphariss]

I did this one like this. It was a rebarrel and I set the liner at the rear of the cup in the cupped breech.
Soft lead in a fine line mech pencil. Drew around the pan cover to make sure the SS liner was not likely to come over the top of the pan cover when closed.  Not important but I did it anyway.


Dan

[bob in the woods]

More room for opinion here I guess.I don't like the vent to be right at the breach face. I like it just a little ahead ofthe face. On a .50 cal I usually pot it about 1/8th inch forward. 
 

[Blacksmoke]

Albert:   I am with Dan on this one.   I prefer the touch hole to be slightly above the the bottom of the pan because it is the first flame in the pan that you want to ignite the powder charge.  Flame will fly faster through a short distance of air than it will following a train of powder.     Historically the criteria was to obtain "sure" ignition not necessarily "fast" ignition. The configurations of flintlocks were designed to create a "train" of powder from the pan to the main charge and thus guarantee a "fuse" type of ignition.  Today we have become accustomed to centerfire with it's immediate discharge of the cartridge.  So we have a tendency to want our flintlocks to do the same.   I also like the ignition point to be behind the main charge which makes  the initial discharge tend to "push" everything forward from the very beginning of the ignition.  That's why I developed the breeching system as illustrated below.  It is also the strongest breeching system ever employed in the construction of traditional muzzle loading.

[okieboy]

 I am with Bob on this one Al. I use screw in vents, because they are replaceable. You can modify one to your heart's content and if you wreck it, just throw it away and grab another. I don't want the face of the breech plug cupped, notched, threaded, or anything but flat, so I layout  the location such that the tap threads will miss the face by .020-.030". I also don't put mine dead at the top of the pan, but just a "smidge" down (smidge=.040-.060". I used to prime "light", but now prime "medium" after reading Larry Pletcher's research. If you haven't read Mr. Pletcher's work, you really should; it will really give you a different view of what is going on at the pan.
 One thing that I have learned on my own is that the freshness of the priming powder is important. I prime with 4F and a pound will last quite a long time, but the difference between old powder well stored and freshly opened new powder is apparent on targets.

[Rasch Chronicles]

Gents,

Thank you all very much for your responses; I learn new and interesting things every time I read a post!

So, the venthole can be placed in a number of spots, depending on your desire and ideas. That makes it much more sensible now.

Blacksmoke, thank you for sharing your drawing, that really helped! Mr Okie thanks again for the details, I'm more mechanical than artistic and numbers make sense to me.

Best regards,
Albert A Rasch

[Dphariss]

More room for opinion here I guess.I don't like the vent to be right at the breach face. I like it just a little ahead ofthe face. On a .50 cal I usually pot it about 1/8th inch forward. 
 

How I do the vent depends of the situation, what I am installing, the breech plug diameter, bore size....



This has a hole drilled right at the breech face that is just a few thousandths over the counter bore in the vent liner. The vent liner is installed to a shoulder that keeps the liner and the bore sealed. I make the vent liner to fit the application.
This is not possible with a thin wall barrel.
The one Hugh illustrated is a good choice and I use them too. I allows putting the fence close to the breech of the barrel.

Dan

[Jerry V Lape]

Dan, the photo has me a little confused - what else is new.  I believe I see a channel across the breech plug face, then a liner stopped against a shoulder in the breechplug.  But I don't understand what appears to be a curved vent hole to the exterior of the barrel?  Would you elaborate please?

[Long John]

Rasch,

Being an amateur I do things a little different from the professionals here.  I build the gun around the vent - not the other way around.  Once I have let in the barrel I locate the vent.  Since I use vent internal cone vent liners I locate the vent location so that the threads of the vent liner just clear the face of the breech plug.  With the vent location clearly center-punched on the side flat of the barrel I dis-assemble the lock and inlet just the flash-pan part of the lock so that the vent hole is tangent to the top surface of the pan ("sun-rise position") and centered over the pan.  Now that the flash pan part of the lock has been inlet I install it onto the lock plate and use it to locate the lock-plate.  This method might offend the artistic instincts of some other makers but I build rifles to shoot and I want to maximize their performance.  With a little planning ahead you can be assured of good flow of the artistic aspects of the gun design.  Usually I end up modifying the shape of the lock plates, cocks, etc. anyway.  It's all part of the design process.

Thank you for your service to our country and the interests of freedom across the world.  Be careful and know you are in my prayers.

Best Regards,

JMC