touchhole location / altering pan shape

[The other DWS]

the last major mechanical installation to do on my "trade rifle" is the touchhole.  I need some input on placement.   I am using the TOTW type C tradegun as the core of my kit with the colraine 54 cal rifled tradegun barrel which comes with the breechplug installed.   the stock comes precarved and because of the half-round half Oct. barrel with wedding bands and the 90% pre-inletted lock my lock and barrel positions are locked-in.
  In using the ramrod to check the breech face location, and also measuring from the breech edge of  the barrel for the TOTW-shop spec of .550 I find that the breech face is very slightly to the rear of the vertical midline of the pan.  Using the "sunset position" gives me a location horizontally just about dead center of the side flat.

As I understand it this would be about ideal for a straight simple drilled touchhole.

However I ordered the TOTW AMPCO touchhole liner with the kit;  and after reading and rereading the touchhole liner thread a n umber of times I also ordered a couple of the Chambers WL liners and tap/drill.

the quandary I face is this:
  If I use the larger Chambers liner,  my preference,  I think I'll wind up with part of the internal cone behind the existing breech face.  If I use the smaller diameter TOTW liners (which is also coned but is significantly smaller cavity)  I might clear the breech-face If I shift the touchhole center slightly forward.    I believe I could remove the breechplug and angle or dish and groove the breech-plug face to clear the preferred Chambers touch hole liner.  However that would not permit breech face scraping for thorough cleaning.
 I think I could use the smaller TOTW liner by slightly altering the pan shape by grinding it slightly forward.
  I could of course just use a plain straight touchhole-- a poor third choice in my mind.

Looking at some of those high-end English pans on the touch-hole thread makes me wonder just how cast-in-stone our ideas of powder pan shapes really are.  Maybe moving it a forward, a bit more "V" shaped, and angled down a bit toward the touch hole end might not be bad.

decisions decisions decisions;   maybe I'll work on the wood for a while longer, see what advice you guys have, and let ideas percolate a bit

[rich pierce]

Many guns have been made with a little ground-out area of the breech face.  I don't like it, figuring it exposes threads and doesn't make as good a seal. For a trade rifle I'd go "natural", a drilled vent, but that's just my preference.  Some folks are reluctant to go with a stright drilled vent hole, which was the common method used by all the original masters we admire.  I bit the bullet and did it on my latest rifle and no regrets.  If you want potentially 10% faster ignition and a little more reliability, I'd go with the liner that won't require you to alter the breechplug.  I've got an ampco liner in my first rifle that works great.

[Gary Tucker]

I have used the ampco liner in nearly every one of the rifles that I have built.  Never had a problem with them.  I always open up the inside cone a tad bit to let more powder in.  If the gun is to be used with 2F powder then I always drill the vent hole a little larger.  That is my normal procedure unless someone just asks  for the Chambers liner [which they sometimes do].

[The other DWS]

I fully intend to use this for my deer hunting M/L so I do want the "improved" ignition. otherwise I'd stick with the straight drilled touchhole.

Any thoughts pro or con on modifying the pan configuration?

[smylee grouch]

This forum is one of the best things to come along for us gun builders in a very long time but it does create a catch 22 type situation by giving us so many choices, good choice backed up by so many very good and experienced smiths and shooters. Your quandry is a good example, you will have some good and bad whichever way you go.  You could pic one method that whould give you the option to change latter or you could pic one and dont look back and just learn to live with what you have.  Good luck whichever way you do it.   Gary

[Joe S]

Maybe moving it a forward, a bit more "V" shaped, and angled down a bit toward the touch hole end might not be bad.

Any thoughts pro or con on modifying the pan configuration?

Larry Pletcher’s data clearly shows an advantage in having the priming powder close to, or even covering the hole.  Therefore, a pan modification that helps keep powder close to the hole is probably a good idea.  It certainly won’t hurt anything.

I am going to modify the pan on the lock I am currently working on.  As you can see in the pictures, there is only a small notch about 0.025 inches deep where the pan contacts the barrel, and the pan geometry tends to keep the powder in the center of the pan.  I’ll open up the side the pan considerably, and if possible, angle the bottom of the pan towards the barrel.

[D. Taylor Sapergia]

I have ground out the pans on a number of locks.  Some locks have a pan that does not extend all the way out to the edge laterally and is also narrow fore and aft.  So I change them to suit the build.  You can remove quite a bit of metal on the leading edge of the pan to move the centre forward, as long as the frizzen's pan cover still does its job.  When you are grinding away in the pan, remember that the foot of the mainspring presses up on the bottom of the bolster and if you go deeper, you could run into that little recess.  Also, be careful with the edges of the pan...don't round them over with injudicious grinding.

[Joe S]

Thanks for the advice Taylor.  I’ll keep that in mind.  I don’t see any need to go deeper in the center of the pan, but moving the leading edge forward is a good idea.  It seems that anything you do to maximize surface area for sparks to land on would be a help for consistent ignition.

I’m not looking forward to this project because it’s a Dremel tool job.   It seems like every time I pick that thing up, I have it get away from me somewhere and it takes a bite out of something I didn’t want it to.

This particular pan is an on an English lock, and was cast directly from the original lock.

[northmn]

I have altered the pan on a lock to be used for a smoothbore but to catch more sparks.  One way I ahve solved the problem you have is to counter bore the face of the breechplug.  I used a 1/2 in drill on my 20 bore.  You can then drill and work in a liner.  It has worked very well for me.  If its a tight fit use a 1/4 inch liner, but work up on drill bits until you get the tap size.

DP

[Roger Fisher]

If she were mine, I'd visit the pow wow lady then get a grip (on the dremel tool) and widen that pan even her out and polish (shine) the ground area.  Heck, it worked for me, then you do not create a cleaning problem on the breech plug face.   BTW I see more shooters that have ignition problems since they can't get it imbedded in their thought processes that they must get that breech clean and prevent that fouling rock build up.  This is a bane to many newer shooters..and some oldies...

[The other DWS]

I'm really reluctant to tamper with the breechplug face.
 I want be able to scrape that puppy clean on occasion so I'd like to get the rear edge of the liner's inner cone right at the forward edge of the plugface; putting the touch-hole itself 1/2 the diameter of the liner ahead of the breech plug face. Thats assuming I understand the preferred geometry correctly.  I think I can adjust the pan enough to accommdate that for the TOTW Ampco liner.  I'm not sure I can squeeze the White Lightning liner in.

Do the liners usually protrude into the bore requiring some reduction of their internal edge?
  I suppose in theory one could take the outside diameter of the barrel where the touch-hole is to go,  and subtract the rifle bore diameter to get the wall thickness at that point.  then adjust the liner's length to fit that thickness.

[smallpatch]

Chamber's also offers a 1/4"White Lightning liner.  Same diameter as the ampco.  Same price as the 5/16 and 3/8"  Would that solve the problem??

[northmn]

Do the liners usually protrude into the bore requiring some reduction of their internal edge?
  I suppose in theory one could take the outside diameter of the barrel where the touch-hole is to go,  and subtract the rifle bore diameter to get the wall thickness at that point.  then adjust the liner's length to fit that thickness.
[/quote]

Some install the liner and file it down from the inside with the plug out.  I use a depth gauge and measure the depth and file it down so any protuberance is minimal.   With my installation the breech plug cannot be removed once the liner is in.   Too much protuberance in the breech is a PITA as it grabs patches when you clean.  I can clean my breechplug faces as I look at them with a bore light after cleaning and can scrape them during shooting.  A slotted shotgun wiper works great for wiping off a counterbored plug.  One of my guns is a fowler made out of a modern gun barrel that uses a modified Nock type breechplug about 1 1/2 inches deep to provide for the chambering dimensions.  The insert is actually drilled through the front of the plug and and the barrel.  It works.  There is also a theory that the lock gate should be even with the back of the breech as common on originals.  to do this you have to do some modification of the breech plug.

DP

[rich pierce]

Agreed, DP, the liner must never grap patches or tow, or it will make ignition much worse than no liner at all because crud will build up.

[rdillon]

How about an all steel I believe 12L14 from Jim Chambers.  Same as a White Lightining liner just not stainless and it disapears when you install it.  Even with a French Gray or in the White you can't tell its there.

Just my 2 cents worth.

[Acer Saccharum]

Rich D, I just bought some steel vents fro Jim. I believe they are 4140, also known as 'stress proof steel' in the aircraft industry. Better by far than 12L14 for this application.

Tom

[rdillon]

Rich D, I just bought some steel vents fro Jim. I believe they are 4140, also known as 'stress proof steel' in the aircraft industry. Better by far than 12L14 for this application.

Tom

Yes, Yes, you are correct. 

Gettin' old isn't for sissys!

That "Sometimmers" stuff is really bad! 

Thanks for reminding me sorry for the mix-up.

[northmn]

Stainless steel is used mostly to prevent premature burn out and to last longer.  The stuff Ampco products are made out of also resists burnout more.  Whether that would be an issue I do not know as many rifles are really not shot all that much and replacement of a liner is not all that hard.  I have made my own out of stainless steel bolts I get from a Hardware store.  Whether the best I do not know but they work. 

DP