need a little help

[jmdavis]

My fowler began to missfire quite a bit in the past couple of weeks. I tried the not cleaning between shot to keep the channel more clear but aft 5 shots, it failed to fire 4 times with fresh 3f priming (3f in the barrel as well).

Since it's never been 100%, I decided to unscrew the vent and see if I had excessive fouling built up on the breachplug. While that wasn't a problem. I discovered that vent liner was only engaging 2 3/4-3 threads when installed and had little counterbore on the inside. After measuring my line (1/4 inch and determining that it was 1/4x28 threaded), I ordered a couple of new ones from Track (after all 2 is 1 and 1 is none, right). I installed one tonight after cleaning the threads in the barrel. It took some shortening with the file on both ends.

Here's my beginner question. The counterbore is insufficient and I can't really file the outside much more. It is flat and bottomed but a few thousandths proud of the side of the barrel. The ultimate solution may be an upgrade to a white lightning or a custom liner since this flash hole is higher than I would like, but is there any safety issue with the liner a few 000 proud.

Thanks for any help you are willing to offer

[Dave B]

What was the touch hole liner you had in there? If is was the same then they must of filed it from the face as well. All that means is it may erode out more quickly from firing making you replace it all over again. I would be inclined to get the counter bore correct first and see what that gets you. Obviously you will need to take alittle more from the other side to allow for the deeper counter bore but the face will be flush now. Good luck with the project.

[jmdavis]

Good advice. I guess after next week I will look at the 5/16 white lightning or get a small parts machinist to build me one slightly off center.

I will see how this one does. The other plug may have been custom. It was definitely flat to the barrel and the slot was deeper than this one. It is the outside counterbore that is the problem now.


Thanks again,

[Dphariss]

My fowler began to missfire quite a bit in the past couple of weeks. I tried the not cleaning between shot to keep the channel more clear but aft 5 shots, it failed to fire 4 times with fresh 3f priming (3f in the barrel as well).

Since it's never been 100%, I decided to unscrew the vent and see if I had excessive fouling built up on the breachplug. While that wasn't a problem. I discovered that vent liner was only engaging 2 3/4-3 threads when installed and had little counterbore on the inside. After measuring my line (1/4 inch and determining that it was 1/4x28 threaded), I ordered a couple of new ones from Track (after all 2 is 1 and 1 is none, right). I installed one tonight after cleaning the threads in the barrel. It took some shortening with the file on both ends.

Here's my beginner question. The counterbore is insufficient and I can't really file the outside much more. It is flat and bottomed but a few thousandths proud of the side of the barrel. The ultimate solution may be an upgrade to a white lightning or a custom liner since this flash hole is higher than I would like, but is there any safety issue with the liner a few 000 proud.

Thanks for any help you are willing to offer

Three threads is dangerous you dodged a bullet. A rifle may have spit this thing out.
Since you have installed a new liner and I am assuming it removable too, remove and drill it carefully to form an inside cone. This counter bore need not be more than 1/8" in diameter,  drill to within about .040 or slightly less of the outside of the liner if you have it filed close to the barrel flat. I would snug it down with reasonable torque for the thread size and file it flush.

Tape the barrel with one layer of masking tape to bring the liner to flush or as close as a layer of tape will allow. The tape will protect the barrel if the filing is carefully done. I would use a 6" 3 square file. Once this is done you should have a very short vent leading to the drilled counterbore. The vent itself can be .062 to .070 diameter and in fact SHOULD be. But larger than .070 should not be needed.
If you are unsure of your skills then contact someone who understands how this needs to be done to check your work.

Dan