leaking gas at the powder drum

[Dave B]

I got a surprise  from my very first scratch built rifle today while cleaning the barrel. My daughter and I went to shoot at a local rondy and when I got home and showed her how to clean the barrel I found water jeting out where it shouldnt around the barrel and powder drum shoulder. It was spraying into the lock mortice area. I would only occasionally clean by removing the barrel and submerging the whole breach. Lately I have been using one of the hose affairs leaving the barrel on the stock. This just blew me away that it was spraying a fine jet under pressure from the down stroke of the  patched cleaning rod in the barrel. I have been toying with rebreaching the barrel with a patent hooked Hawken style. I guess it is time. I don't shoot this rifle much and have been thinking to leave it a lone as being my very first built rifle. Yes I could just put in a larger powder drum and keep her as how bad I really was when I first started. I think the biggest thing for me right now is knowing there is a problem that could have been very bad down the road but was caught by some high pressure water cleaning. 

[Roger Fisher]

That sounds as though she is gas cutting and it will only get worse til the drum decides to part company with the barrel.   In the bush by yourself that would be bad news; but at a line shoot with other folks on your lock side it could be a disaster.

If the drum thread section is a quarter incher (doubtfull) or a 5/16th you could retap the threads and go to a 3/8th.  What size barrel?  Its good you found that leaker.

Convert her to a flinter?

[Dave B]

You are so right on that. The barrel is 15/16 and the drum is a 5/16 if I am not mistaken. I will take it out to the 3/8 for now. I confess That pulling the lock out and putting in a late Ketland did pass through my mind. I have a hooked flint breach in my parts box that could be put to good use.

[Dphariss]

I got a surprise  from my very first scratch built rifle today while cleaning the barrel. My daughter and I went to shoot at a local rondy and when I got home and showed her how to clean the barrel I found water jeting out where it shouldnt around the barrel and powder drum shoulder. It was spraying into the lock mortice area. I would only occasionally clean by removing the barrel and submerging the whole breach. Lately I have been using one of the hose affairs leaving the barrel on the stock. This just blew me away that it was spraying a fine jet under pressure from the down stroke of the  patched cleaning rod in the barrel. I have been toying with rebreaching the barrel with a patent hooked Hawken style. I guess it is time. I don't shoot this rifle much and have been thinking to leave it a lone as being my very first built rifle. Yes I could just put in a larger powder drum and keep her as how bad I really was when I first started. I think the biggest thing for me right now is knowing there is a problem that could have been very bad down the road but was caught by some high pressure water cleaning. 

This can happen with nipples and vent liners as well.
Much of this is due to the slop built into modern taps. The threads will pass gas and liquids. Oil will seep out and soak the wood.
The OUTSIDE SHOULDER must be seated flush and tight on the barrel flat to prevent this. OR the drum can be seated against an INTERNAL shoulder as well
With a drum I am surprised that the nipple does not leak as well. Even patent breeches will leak at this point if they lack a flat to seat the nipple tightly on.
If the hole in the side of the barrel is not exactly 90 degrees to the barrel flat it will likely leak. A larger drum may make it worse rather than better unless the hole is "straightened".
There are people here who will tell you that seating on shoulders or chamfers is unnecessary. Mostly because they don't want to take the time to do it. But this is an integral part of making a quality firearm. It prevents the problem you are experiencing. Along with fouling traps the will hold oil and fouling and can cause reliability problems
Your experience is just another reason not to use a Drum and Nipple.
Your SAFEST course is to cut the barrel to the proper length and install a good patent breech (check that nipple seat). It need not be a "Hawken" breech.

Dan

[Steve-In]

Much of this is due to the slop built into modern taps. The threads will pass gas and liquids. Oil will seep out and soak the wood.

 
Unless it is a tapered pipe thread it will not seal.  Dan is correct in that you need to have a shoulder to seal against.  Pipe dope and tape is really just a bandaid at best.  You need to get your taps from a source other than Sears or the local hardware store.  Greenfield, OSG and Vermont are good brands.   I use a .03 wide groover in a lathe to face the shoulder and undercut material that cannot be threaded.  I also go minimum on the chamfer on the barrel to get the max surface on the shoulder.

[Steve-In]

Below is a link to tap questions.  At work I deal with threads every day in aluminum bar, cast aluminum, ductile iron, stainless steel and CRS and hot rolled steel.  We use both cut and form taps as well as thread mills.  The leading cause of gaging failure (oversize threads) is dull taps.  Followed by bad TIR (the tap wobbles) and hole size.
Another thought is the drum may have been undersize and caused the failure.
http://www.newmantools.com/taps/taptech.htm

[Dave Faletti]

The threads can't be cut full all the way to the bore.  Even with the best taps there is still a gap.  The first 1 and 1/2 threads from the bore should be an interference fit.  Boths end of the thread need to be sealed or it will corrode. As already mentioned it will errode as well if it doesn't seal somewhere.

[Dave B]

Thanks for the thoughts guys. I will be more careful in the future when it comes to the use of taps. I have improved since this rifle was built and have not had any trouble from my new work.

[Pete G.]

There is also a possibility that the drum is cracked at the step where the shoulder meets the threads. I saw this once before and it seemed to have occur ed because the drum was fit a little too closely to the lock plate. When the barrel was snugged down into the stock a lot of pressure was put on the bottom/rear of the drum and there was a crack in this area. Maybe the barrel had set back just a tad over the years from the effects of recoil? Who knows? Just illustrates the importance of a thorough inspection now and then.