Moving flash hole

[columbia]

I purchased a used Tulle 20 guage lovely gun but touch hole liner off center (too far foward maybe by 3/32") in relation to center of pan,
height is correct. Prone to flash in the pan when gun is left loaded for a time, failed to fire at turkey yesterday fired when reprimed. Same thing happened a week before. I have another flint I built never fails to fire when first loaded during a hunt. I have followed same loading procedures for both using a pick etc., different charges of course.
I want to reposition flash hole properly. Can I replace vent liner (mine is 1/4" vent liner) with a bolt and drill it center to pan which will wind up in the threads? Or tap a bigger hole 3/8" and and drill it so hole is centerered to pan The current liner has no hollowed out area inside to bring powder closer to pan my gunnsmith hollowed it out will that do the trick?
Thanks in advance
Jeff

 

Lots of schools of thought on the placement the flash hole as to forward , back, center . The only stead fast rule that I know of is top of pan or slightly above .
I personally have a rifle that has the hole forward as you say , fires very well and most all the time , when it doesn

 

[Packdog]

Can you widen the pan? Just make sure the frizzen will still cover the pan when closed. I'd do that before I tried moving the liner. Unless it is way forward the coning may do the trick. I have one that is a little forward and never saw it caused any problems?
Packdog

 

[tg]

If the hole is 1/16" I would go to 5/64" and see if that solves the problem.

 

[Zonie]

jensenkill: Another thing to check on before getting the ole Black and Decker out to reposition the touch hole liner is where is the face of the breech plug in relation to the touchole?

The center of the liner has to be 1/2 of the diameter of the liner threads in front of the breech plug face. If it is further aft, the vent liner threads will run into the breech plug face (if it is in place when it is tapped).
If the breech plug is pulled, and the new vent liner threads are behind the face of the breech plug, even if the vent liner is shortened so it don't interfere with the breech plug , the breech plug will not seal properly against the back of the bore.

This becomes even more of a factor if you plan on enlarging the vent thread size. In fact, enlarging the vent threads may cause the center of the threads (and the vent hole) to move forward, relative to the lock.

The best idea was mentioned above. Widen the pan on the forward side some.

Although I don't have any high speed pictures to proove it, IMO, if the vent is within 3/32 of being centered horizontally with the center of the pan, and the vent liner has at least a 1/16 inch hole in it, the gun should fire reliably.