Breech plug thread depth

[frontstuffer]

Need some advice, started building a Early Lancaster rifle, Green Mountion barrel 1" across flats, 42" long, 54 cal., 3/4-16 x 5/8 deep breech thread. Using a Jim Chambers Sliver flint lock. I have read that if the breech plug depth is deeper then 1/2" you will have difficulty placing the rear lock bolt. The vent hole position will force the lock to far forward. Do i remove 1/8" from the breech end of the barrel bring the breech depth to 1/2" deep or keep the 5/8 depth?.

Thanks in advance.

Mark

[Jim Kibler]

You could shorten it, but it won't make much difference in how it looks in the end.  I get the feeling you are just starting and there are many more important things to consider.  There are many examples where the fence is in front of the back of the barrel as well.  My advice...  Don't mess with it.

[greybeard]

I would not mess with it either. Just make sure it is bottomed on both face & back of the plug.
It would be a good plan to do a real size drawing of all the components in the breech section and their relationship to one another..  Leaving the plug 5/8ths may mean drilling a hole in the breech plug rear lug for the lock bolt but that is very common. Good luck   Bob

[ottawa]

if you shorten the breech end of the barrel then the plug mite not go flush or line up right as what has been said earlyer is your best bet (other postings)

[T*O*F]

Well, just to be contrary I disagree with everyone else.  It's no harder to install a 1/2" long plug into a 1/2" deep hole than it is to install a 5/8" long plug into a 5/8" deep hole.  Inexperience has nothing to do with it so you might as well get it under your belt now because the hard part is clocking the plug correctly, not the length of the threads.

I don't care to start a discussion on lock placement, but I prefer the fence to be lined up with the back of the barrel.....personal preference cause I don't like that little stub of wood hanging out in the middle of nowhere.  I have guages made from allen-head plugs for various locks.  I screw the plug into the breech and file the barrel flush with the head of the plug.  Then place the plug against the breechplug and cut off the protruding threads.  Then I clock the breechplug.  It's no big deal.

You are not building a gun.  You are performing a series of small operations, which when completed result in a finished gun.  You need to learn how to do each small operation proficiently and spend time considering its effect on the finished product, because many times an early step will cause problems with a later step.

[Herb]

Mark, absolutely cut it off.  It makes the lock location much better.  To help you, see the Tutorial Board, my post of July 07, 2010, now down on page 3.  Subject "Fitting a Hawken Breech Plug by Hand".  Yours is a plain flint plug and not a Hawken, but  how to cut off the barrel and fit the plug is the same.  Greybeard's suggestion to make a full-size drawing of the location of the parts is very good.  Draw it both ways, 5/8" and 1/2".  And T*O*F's use of a breech plug gauge is also very good.  I have cut off a bunch of Green Mountain barrels, from 5/8" to 1/2".  Rice barrels are all 1/2" plugs, actually .550.  I just pulled the plug on a 7/8" .50 Rice barrel and fitted a Hawken Squirrel breech plug, 7/8" but only .500 long, to make a smaller size .50 Hawken for a woman.  You can do this work on your breech plug.

[Dphariss]

Need some advice, started building a Early Lancaster rifle, Green Mountion barrel 1" across flats, 42" long, 54 cal., 3/4-16 x 5/8 deep breech thread. Using a Jim Chambers Sliver flint lock. I have read that if the breech plug depth is deeper then 1/2" you will have difficulty placing the rear lock bolt. The vent hole position will force the lock to far forward. Do i remove 1/8" from the breech end of the barrel bring the breech depth to 1/2" deep or keep the 5/8 depth?.

Thanks in advance.

Mark

You will likely have to notch or drill the breech plug tang for the lock bolt anyway.
The depth is not so critical, though I like shorter plugs over longer ones, the FIT is.
The breech face should seal the bore.
I use magic marker to color the breech face. When breeching a rifled barrel the color should be wiped off except where the lands are as shown in this "cupped" breech face for a 58 caliber barrel.


Or this breech being made for a 50 caliber smoothbore barrel.


Internally it should look like this 54 caliber barrel.



The photos below are of a sloppily made breechplug and the breeching it creates.

The breech face should NOT look like this.


Or internally like this, massive fouling/oil trap.

[Dphariss]

I will agree that there are original rifles with the fence well in front of the breech face.
There are a lot of things done on original guns that create a less than pleasing effect.
I try not to recreate these things.
One of my criteria is "don't copy ugly guns". There are too many good ones.
In a quick look through RCA we see very few that are as far forward as is found on most precarved stocks  with a lock inlet  today, these are almost all are set up for a long breech plug with the vent in front of the breech face.
Its done for ease of assembly not to make the gun look right. Sure its possible to make a good looking rifle with a lock 1/4 or 5/16 gap between the fence and the breech. But its still clumsy looking to my eye.
Looking at most Dickerts, most JP Becks, the Schreit rifle  etc etc have the fence at or very close to the breech.
So I like shorter breechplugs.

Dan

[Jim Kibler]

I'd forgotten that a Green Mountain plug isn't factory fit.  You could shorten the thread lenght to 1/2" if you wanted to and felt comfortable with the job.  I do agree that it would be a touch nicer if shorter, but not a huge issue when compared to all the other things to get right as a new builder.

Jim

[coutios]

Mark, As you can see the topic "to shorten or not to shorten" is a very sore subject with some. That's a choice you can make on your own. There is no right or wrong way..  BUT.. There is a right or wrong way to breech a barrel. If you are comfortable in your skills and choose to shorten than go for it. On the other hand if your not so sure.. You could breech it at 5/8, if your happy, than ok get the saw and go for 1/2...  The most important thing is to get the proper seal...

Just .02 cents more

Regards
Dave

[Dennis Glazener]

I think his concern is not about where the fence ends up but about hitting the web with the front lock bolt. If I remember correctly on the last Chambers kit I did there were dimple's on the side plate for where the lock bolts go.  It appears to me that moving that spot 1/8" forward for the 5/8" breech plug would not cause a problem hitting the correct spot in the web. But what about the side plate, isn't it also semi-inlet in the wood? If so will having everything 1/8" forward of where it was designed to go cause problems? Will the semi-inlet sideplate mortise be in the wrong position? Will moving the lock bolts forward put the lockplate too close to the edge of the wood? If the kit was designed for 1/2 inch breechplug I would cut the breecplug back to 1/2" so everything else lined up were Chambers intended for it to go.

I would think that a 5/8" threaded plug would be no easier to time than a 1/2" one. The only difference would be the actual shortening of the threads and I wouldn't think that would be too difficult. What am I missing?
Dennis

[frontstuffer]

Thanks for the interesting advice, the build is from a blank, so far have only inlet-ed the barrel and drilled the 3/8 ram rod hole. This is only my 3rd. build from a blank (1) G.R. Douglas and (2) G.M. barrels and all have been 1/2" depth.
I have access to a full machine shop so removing 1/8" from the barrel and fitting the breech plug is no big deal. I was hoping to save some time if the 1/8" was not a big deal. After reading all the replies i will go with 1/2" plug. Every build is a learing experience for me. Thank's again for the help, hope to post some pic's. in the future.

[Herb]

Good on you.

[Dphariss]

Thanks for the interesting advice, the build is from a blank, so far have only inlet-ed the barrel and drilled the 3/8 ram rod hole. This is only my 3rd. build from a blank (1) G.R. Douglas and (2) G.M. barrels and all have been 1/2" depth.
I have access to a full machine shop so removing 1/8" from the barrel and fitting the breech plug is no big deal. I was hoping to save some time if the 1/8" was not a big deal. After reading all the replies i will go with 1/2" plug. Every build is a learing experience for me. Thank's again for the help, hope to post some pic's. in the future.

I you have a lathe and mill it is pretty easy to make the plug from round stock fit it the internal shoulder and the fit to the breech end of the barrel. Then tighten it to assure it will maintain its "fit" I wok this in back and forth several times. Making SURE its seated well on that inner shoulder. Once you are sure everything is right then machine the top tang flat then machine the plug to shape.
This allows putting the top flat where the builder wants with no "indexing". It makes a lot of chips true but I like doing it this way.
The is the process. But these are not being fitted. I am making some plugs for 1 1/4 barrels for a couple of friends.



These are annealed cold rolled.



Dan

[Dphariss]

PS a tapered end mill will help in profiling and in the initial inleting the breech plug.
Dan