New member with a breech plug issue

[Bradley Combs]

I am using a Colerain .45 caliber 13/16'' barrel and a breech plug from Track. As my first building task, I fitted the breech plug. I followed the method in Wm. Buchele's Recreating the American Longrifle, using Prussian Blue and a mill file to fit the plug.



Buchele writes that the forward faces of the tang and lug should contact the rear face of the barrel. As you can see, mine do not. You can still see a sliver of daylight between the two faces.



The plug will no longer pick up any Prussian Blue and I don't want to shorten it any more than necessary. Here is the plug itself. I haven't filed the face at all. Just where the blue picked up.



Interestingly, the plug did not turn out symmetrical.




From the rear face of the breech, I measured between .548'' and .570'' to the shoulder at any point. I believe this is why my plug turned out lopsided.

I am concerned about the faces of the lug and tang not touching the rear face of the breech. It is written that they should. I do not know how to achieve this. I also do not know how to proceed with the face of the plug. It's somewhat domed now around the edge, and will not pick up any layout fluid when installed. What should I do?

[rich pierce]

I'd go 1/8 more turn with it. Something is preventing it going in farther. Must be touching the face somewhere. The lopsided ness is ok, am sure plenty of originals were imperfect. You want no gap at huge top flat.

[EC121]

I agree with Rich.  The top is in closer than the bottom so one lick with a file should get it to the next flat without the bottom hitting first.  Smoke the  breech end of the plug and see where it is hitting.

[Dennis Glazener]

I may be wrong but the face of the tang (the area that butts with the very back of the barrel) does not look square to me. You may have to use a file at the base of the tang/breech threads. If I am right the bottom of the tang/breech face may be hitting the barrel but the top is left with a slight gap. Hope this makes sense.
Dennis

[Sidelock]

Here is a trick I use to get a square face on a plug I am indexing - Make a jig out of a piece of 3/8" cold rolled steel - say 1.5" X 4" would do.  Ensuring you are exactly square to the surface, with a drill press - drill a tap hole of the correct size for your breech plug size and tap out the hole (use a piloted tap in a drill press again to ensure your are square with the surface of the jig).  Now you got a 3/8" deep hole you can screw your breech plug into. If you need to remove say .02" from the face of your plug, screw it into the jig until that amount mic's above the surface of the jig.  Clamp the jig with the breech plug in it, into a vice and file the face of the plug down until it is flush with the surface of the jig.  Doing this gives you a square face to your plug, pretty easy.  Take that same jig and drill other holes for the various common sizes of breech plugs, tap them out and save that jig for future projects. Hope this helps.   

[rich pierce]

Sidekick, this is a good technique.  I would even go so far as to case harden the tool if I was going to do much breeching.

[Mark Elliott]

The breech plug face has to be hitting somewhere,  probably on the edge.   I use permanent marker on the plug face (and thread face) and the face of the barrel where it hits the tang/recoil lug.   I turn in tight and look for where the marker was knocked off.   That is where I file with a Swiss #0 pillar file.   If you are careful,  the lopsidedness will work its way out, little by little.  Hand fitting a breech plug can be very tedious.  You still have plenty of plug you can remove.   Don't even start to worry until you have less than .5" of threads.   I like to finish at .5" and will cut one thread over that if the plug is long.   Then I will start fitting.

You might put a little white lithium grease on the threads to help you turn it in.    I suspect you are either not turning the plug in tight enough or you are missing where the plug face is hitting on the edge.    

Another thing,  the barrel needs to be clamped in the vise right at the edge of the breech so that you don't twist the barrel out of the vise.   Also,  you will need lead liners on the vise jaws to get a tight enough grip on the barrel.   The arrangement I see in the photo with the barrel wrapped in a rag will not work.   If you aren't twisting the barrel out of the vise with that setup,  then you aren't putting nearly enough torque on the plug.   You also need a nice tight fitting wrench.   I have an adjustable wrench with jaws ground to fit the V shaped recoil lug.   I also have a forge made wrench for larger plugs. 

[Ky-Flinter]

I may be wrong but the face of the tang (the area that butts with the very back of the barrel) does not look square to me. You may have to use a file at the base of the tang/breech threads. If I am right the bottom of the tang/breech face may be hitting the barrel but the top is left with a slight gap. Hope this makes sense.
Dennis

All good info and I agree with Dennis, the second picture seems to show the upper tang face isn't square.  Old William B. was right, ideally the plug face will contact the "step" inside the barrel where the riflings start, at the same time the upper and lower faces of the tang contact the back of the barrel.  The plug face to step fit is critical.  The upper tang face to barrel fit is cosmetic, but will look real bad if not tight.  If you can get the lower tang face tight or close, great.  If not, don't sweat it, a gap there won't show and won't hurt anything.

-Ron

[jerrywh]

 Most of the time you have to relieve either the rear thread of the plug or the first thread in the barrel. The rear thread on the plug cannot be cut to full depth with a tap or even on a lathe. So they need to be relieved. I hope you understand what I am trying to say.

[Curtis]

A log of very good and pertinent advice here, but I have to give a +2 on Jerry's comment about relieving the last thread on the plug (you can do it with some careful file work) and +2 on Mark Elliott's advice on a tighter clamping arrangement for the barrel.

Curtis

[Jerry V Lape]

If you want a really good grip on your barrel try this.  It is a couple of blocks of hard maple with matching center sawed out so the blocks can surround the barrel.  Wrap the barrel in saran wrap fill the space with enough Bondo so that when clamped the bondo takes the shape of the barrel a little forward of the breech plug and put a thin layer on the mating surfaces of the blocks.  Let it set overnight.  Now you have a barrel wrench that fits that particular barrel.  I slide them off the swamped barrel in one piece.  You could choose to not bondo them together.  Mark each one you make for the particular barrel it mates. 

[Acer Saccharum]

It looks like the threads closest to the shoulders are not complete threads. These won't screw into the barrel.

As mentioned above by Jerry, those threads need to be relieved, and this is usually done on the lathe when the plug is being made. Now it's hard to chuck it up without making a special fixture.

You should be able to file around the base of the plug to get it to enter completely into the barrel.

[Acer Saccharum]

Buchele writes that the forward faces of the tang and lug should contact the rear face of the barrel. As you can see, mine do not. You can still see a sliver of daylight between the two faces.

Screw in one more flat, and the top part of the tang shoulder will contact the barrel. Turn the barrel over and peen the lower tang lug to close the gap, with the barrel on an anvil, or suitably heavy support.

[Mark Elliott]

Tom,  you might be right with your last advice regarding the use of a hammer and anvil, but it made me shudder.   

[Willbarq]

The breech plug face has to be hitting somewhere,  probably on the edge.   I use permanent marker on the plug face (and thread face) and the face of the barrel where it hits the tang/recoil lug.   I turn in tight and look for where the marker was knocked off.   That is where I file with a Swiss #0 pillar file.   If you are careful,  the lopsidedness will work its way out, little by little.  Hand fitting a breech plug can be very tedious.  You still have plenty of plug you can remove.   Don't even start to worry until you have less than .5" of threads.   I like to finish at .5" and will cut one thread over that if the plug is long.   Then I will start fitting.

You might put a little white lithium grease on the threads to help you turn it in.    I suspect you are either not turning the plug in tight enough or you are missing where the plug face is hitting on the edge.    

Another thing,  the barrel needs to be clamped in the vise right at the edge of the breech so that you don't twist the barrel out of the vise.   Also,  you will need lead liners on the vise jaws to get a tight enough grip on the barrel.   The arrangement I see in the photo with the barrel wrapped in a rag will not work.   If you aren't twisting the barrel out of the vise with that setup,  then you aren't putting nearly enough torque on the plug.   You also need a nice tight fitting wrench.   I have an adjustable wrench with jaws ground to fit the V shaped recoil lug.   I also have a forge made wrench for larger plugs. 

  So you just use a sharpie? Was thinking of doing this.

[jerrywh]

You can also cut out the last 1/2 thread in the barrel.

[davec2]

Bradley,

Do you have access to a lathe?

[WKevinD]

I agree with Acer that the threads closest to the barrel/ last on the plug look to be the problem.
If that is the case why not a lite "countersink" on the end of the barrel? Then apply torque and check the breechface for even contact.

[JCurtiss]

If you want a really good grip on your barrel try this.  It is a couple of blocks of hard maple with matching center sawed out so the blocks can surround the barrel.  Wrap the barrel in saran wrap fill the space with enough Bondo so that when clamped the bondo takes the shape of the barrel a little forward of the breech plug and put a thin layer on the mating surfaces of the blocks.  Let it set overnight.  Now you have a barrel wrench that fits that particular barrel.  I slide them off the swamped barrel in one piece.  You could choose to not bondo them together.  Mark each one you make for the particular barrel it mates. 

Clever idea there, Jerry.

[Jerry V Lape]

JCurtiss, not my idea.  Picked it up from someone on here years ago.

[Willbarq]

So let me get this straight.

1. Paint the shoulder of the breech in the barrel.
2. Wind in plug tight , but not super tight
3. Remove plug , observe breech plug shoulder and face.
4. file off high spots (smears and bare)
5. Wipe plug clean and repaint breech in barrel.
6. Repeat until the breech plug ends up on the flat you want and the Prussian blue has marked all around the breech plug shoulder. It has to be touching to transfer one to another.

Please correct me if I have this process backwards or wrong!

[Mark Elliott]

So let me get this straight.

1. Paint the shoulder of the breech in the barrel.  -- No.   You paint the breech plug face and the oustside breech that contacts the recoil lug.
2. Wind in plug tight , but not super tight  --  Nope.   Always as tight as you can get it.
3. Remove plug , observe breech plug shoulder and face.    -- Partly right.   look at the breech plug face and the outside breech of the barrel that contact the recoil lug.
4. file off high spots (smears and bare)  -- Yes.   You file the bare spots on the breech plug face and the breech of the barrel.
5. Wipe plug clean and repaint breech in barrel.  -- There ia no need to wipe anything clean, at least I don't using marker.
6. Repeat until the breech plug ends up on the flat you want and the Prussian blue has marked all around the breech plug shoulder. It has to be touching to transfer one to another.    -- You want a bare ring around the outside of the plug where it is hittlng the shoulder and you want the tang/recoil lug pulling up tight against the outside of the breech.

-- I would use permanent marker instead of Prussion Blue.  It is much less messy.  

Please correct me if I have this process backwards or wrong!

[Acer Saccharum]

Prussian blue smears, it's often hard to tell where the contact is when you are screwing the parts in and out again. The evidence gets muddled.

Magic marker is my go-to tool for breech fit ups. It dries instantly, goes on so very thin, and shows the mark with no guesswork. And it doesn't get all over everything.