vincent project

[Leatherbark]

On my 40 caliber Vincent (rebuild/finish what someone else started) the lockplate barrel configuration was not started correctly for installing the drum in the 13/16ths barrel in front of the breechplug.

So I had to install the drum through the barrel into the breechplug and drill a communication hole (a la CVA type patent breech) to mate up with the drum..........Worked out A ok so far and got full engagement of the drum threads..........Bob

 

[ron ward]

excess650,
i don't think vencent used patent breeches on his guns. i have never seen one on any of the few original example i've been fortunate enough to see.

leatherbark,
on another forum there was just a thread about that very problem. one that was done a few yrs ago. the poster said that eventually he started having gas leakage where the the plug is threaded into the breech at the point where the drum hole intersects with the breechplug/barrel because there are so many little crevases for flame to torch away at in that spot. i guess i'd keep an eye on it. the thread went on to say that the best fix would probably be to cut the breech end off and install a new plug.

 

[zampilot]

There is another thread that states someone did a carefull job of fitting and indexing, then sweated it in as it was final installed.

 

[ron ward]

zampilot,
this is just an opinion based on allot of experience soldering, brazing and 25 yrs. as a certified welder.....
sweating the drum in is a decent remedy for keeping it from losening on it's threads because the solder fills the voids that make the clearances needed for the threads to mesh so they don't get get banged around and loosen. but the main problem, from what i understand, is actually the close proximity of the two threaded holes. as said earlier, when ignition happens and temps and pressures rise criticly right at that junction of drum and plug, the creavases that are left by the threads are actually little passages for the flames and hot gasses to travel in. i don't think the solder has a high enough melting temp to stop the gasses from slowly torching the solder out of the threads and eventually the problem will re-appear. that's the reason why i think it is best that the breach plug be replaced by cutting the barrel and making new threads. then re-drilling the drum hole in the correct position.it's also the reason that the face of the breach plug should be shouldered against a seat inside the barrel. the drum is then placed about 3/16 in front of that and there is smooth full thickness material to resist the gasses' torching effect.
just as an observation, not directed to anyone...i think, allot of times we think our predecessors did allot of stuff, "by the seat of thier pants", so-to-speak, but i think they had stuff pretty well thought out, knew more than some of us give them credit for and did things the way they did for a reason. consider,... in the late stages of the percussion era we had guns that would hit thier mark at 1000 yds. in the right hands....no different or better than today.

 

[Leatherbark]

In my case cutting the barrel and relocating the drum was not possible as the lock mortise/barrel breechplug relationship was already screwed up. My only options were to scrap the stock (crying shame as it was a tiger maple with nice inlays already done by the original builder) or slice some threads from the breechplug in order to place the drum in the correct position. I didnt like that idea so I used a 9/16ths breechplug that seemed longer in relationship to the width than a 5/8ths inch.........I installed the 9/16ths plug fully into the barrel using "Red heat resistant silicone" on the threads. But before that I drilled a communiation hole (1/4")about 5/16ths inch deep in the face of the breechplug. When I drilled and tapped the drum to connect with this hole its 1/4 inch hole was position real close to the face of the breechplug and used the red silicone on those threads also.....and the drum indexed and tightend perfect.

So now my breechplug is locked in like a CVA with a small "patent type breech". It seems like this would be safer than drilling into the side of a 13/16ths barrel in front of the breechplug face and having to shorten the drum threads to keep them from protruding into the 40 caliber bore?


Bob

 

[ron ward]

yup , that sounds like it should work fine. i often thought about making a "patent breech" of sorts, that way. it really does give the drum a good bite for stability because the full length of the drum's threads are are used and is allot less expensive than the real mcCoy. my thought would be use a countersink bit on the face of the plug to create a large funnel for the charge to sit in. the cone shaped "chamber" might help with initial flame distribution and accuracy, as well. if you stop the coutersink so the point is right at the back of the drum hole, you have a nice funnel for ignition to propagate evenly. the more i think about this, the more i think i might try it on this build.
probably nothing new. in fact, we are probably talking about just how the patent breech was arrived upon.

 

[paulvallandigham]

I had an imported .45 cal. rifle with a drum ignition. The barrel was thin- no more than 3/4 inch, but the threads on the drum's shaft were FINE, not coarse. I believe that the use of the fine threads was sufficient to support the drum so it posed no danger of coming out. If you have three complete threads on the drum's shaft making contact with the side of the barrel, I think its strong enough.

It always helps to support the outside of the drum with the top edge of the lock plate. My rifle's lock plate was close, but did not actually support the drum. There was daylight between the plate and the drum. :thumbsup:

 

[ron ward]

maybe i'm thinking overkill on the support, i don't know. it may be that there is enough shock absortion in the minute movement of the barrel in it's channel and the crush of the primer that a contact fit of drum and plate isn't absolutely necessary. if the fit can be achieved though, i would think it would certainly be better....especially on a light barrel. and of course, fine threads on the drum is a given. it does require a good fit between lockplate and stock as well. the key to my idea is that with what is currently on the market, you must start with a lock that has no drum notch to begin with so that the drum can be located by the pilot on both plate and barrel at the same time. the problem with all the market sold plates is that the pilot has to be drilled half on and half off the lock plate... not easy, dare i say impossible, to do.
another remedy might be a drum sized ( or drum notch sized) mandrel that would allow a pilot drill to slide inside it precisely. one could then hold the mandrel in the notched plate and pilot the drum hole in the barrel once plate, barrel and tang are fully bedded and the barrel is is pinned in the stock. the opportunity and possibility for the lack of good support right there bugs me!...probably another reason the patent breech came along.