Loose/poorly fitted breech plug

[Daniels48]

Hi all,

I have made a mistake in my Baker build... I fitted the breech plug, marked the face to check fit, filed, repeated until I had even contact inside the bore, tightened it in and continued with the build. Drilled the touch hole, cut the sights in etc.

I took it apart to drill the powder well in the plug a bit deeper which all went fine and I put it all back together and found that I could tighten it further. I have no idea how/why this happened (perhaps there was a thin bit of material where the edges of the face of the plug interfaced with the barrel that wore/crushed down?) but I am now faced with the issue that the plug is only just hand tight when in the right position to fit the stock and sights etc. If I tighten it down with a wrench, the barrel is then canted off to the left.

My questions are - is this safe? So it is only hand tight when firing (I can spin it out by hand). If not, can anyone think of a way to 'shim' either the plug, or the inside of the barrel so I can get a tight mechanical fit inside? I was thinking of cutting a very thin ring of lead and crushing it into the gap so the breach plug sits in the correct location, whilst being tight?

Any thoughts or help would be greatly appreciated. I test fired the barrel (with a fuse, held in sand) with the plug screwed all the way in with 95gr powder and it was just fine, but I don't want to blow myself up by loosening it a little to get the barrel to line up.

I am massively kicking myself for not spending more time on the plug. Maybe I could have spotted this sooner...

 

[LawrenceA]

Could you not take it round a full turn and refit?
I would not use lead as a spacing washer.

 

[Daniels48]

I think I could, but then I'm not sure if the lug would fit into the tang securely... That's a good idea though. If I can't space it with anything, that may be the way forward.

Someone suggested that as long as the tang stops it spinning out when fitted, then it is safe to leave it as is as it has 6+ threads engaged , but I am not so sure

 

[LawrenceA]

The problem is likley that fouling will get into the breach threads and cause corrosion.
A lot of original breechplugs were only about 3/8" long but modern ones are much longer

 

[Daniels48]

I have just taken another look and I think your suggestion will work well, trim it down so it does a full rotation. There is more room to play with than I remembered so I will give this a try

 

[LawrenceA]

Don't rush.
See what others say.
Just take it easy and go slow slow.
As it is a hooked breech there is another option.
Get the right size bolt.
Screw it in, cut it off and fashion the hook.

 

[Phil Coffins]

I’d agree, at this stage a new plug is the prudent route.

 

[Rifleman1776]

I was thinking of cutting a very thin ring of lead and crushing it into the gap so the breach plug sits in the correct location, whilst being tight?

I wouldn't use lead. Get an old, pure silver, coin and pound to make thin and use that as a seal. I believe some old, high end, cased guns have silver, platinum or gold washers between the breech plug and barrel.

 

[pilot]

Copper would probably work, too.

 

[Musketeer]

Copper would probably work, too.

I was thinking maybe a copper crush washer could be installed and fitted to work. They are available in a whole bunch of sizes.

 

[pilot]

I was thinking he was talking about a standard type breech plug, not a hooked breech plug. I don't see a good surface there for a crush washer to bear against. The replacement plug sounds like a better idea.

 

[Larry (Omaha)]

I was thinking he was talking about a standard type breech plug, not a hooked breech plug. I don't see a good surface there for a crush washer to bear against.

You are not going to see via the photo. The poster is referring to the step up shoulder inside the barrel at the end of the threads.
Hope this helps.
Larry

 

[russellshaffer]

Loctite makes a stud and bearing mount product that is really tough. Would this maybe be an option?

 

[old ugly]

if you can get a full rotation then the top of the hooked breach will be tighter in the tang, but the bottom will be loose. so once you have the breach plug tight, hook it into the tang and see. you may need to file the top a bit so the barrel will slid down, once you get to that point if the barrel is loose because of the bottom of the breach plug not making contact you may have to weld the opening of the tang or pull the breach plug and build it with weld and file it to fit.
these are my thoughts on it, not saying it is correct but it is probably the way i would make it tight.
ou
tom

 

[Scota@4570]

Do not make an internal washer. Using dissimilar metals in a corrosive environment will lead to corrosion.

Run it in on more turn. This time use moly paste or resizing lube to prevent galling. When you get close run the plug in and out to fully form the threads to each other. Depending on the thread fit You can gain about 1/8 of a turn as the two parts conform to each other.

And that is what happened. When you first got resistance it was because the thread fit was not great. Whatever was holding it up was worn down or reformed as you took the plug in and out.

If it is properly seated on the internal shoulder but you can force it a little past clocked, it may be OK. Goop it up with antiseiz and move on. ML breech plug do not need to be gorilla strength tight.

 

[ohio ramrod]

I have often fixed the same problem by punching a "shim washer" out of brass shim stock to "fill the gap". It may take you two or three trys to get the right thickness. I usually start with .oo3 and work my way up. Don't try "stacking them as the thin stock will bunch up, just go to thicker stock if needed.

 

[Daniels48]

Thank you everyone for the very helpful replies! I did some more research/digging and found numerous references to using a corrosion-resistant metal as a washer. I tried/did/researched the following and came to these conclusions:

1. I am in Europe so getting the correctly sized imperial bolt in a suitable metal is actually more difficult than I imagined, so other than turning my own plug on the lathe, this is my last option (they are out there and I will keep searching, but some of the suppliers are questionable here)
2. I contacted the barrel manufacturer asking if they are able to ship me a plug but they fit them to the barrel at the factory so this won't work (I may get the same issue with the new plug...)
3. The washer idea is the easiest and smallest risk, so I am going to give this a go with the most resistant material possible and try and crush it in place (without galling) to minimze the risk of corrosion getting into the gaps. I am concious of the risk of corrosion though... If this does not work then;
4. Trim the plug down and do a full turn. I would need to file the tang down, but this is my second choice

Thank you everyone. I knew I would get some very helpful replies on here. Unforutnately, nobody around my area specialises in this sort of thing, so I have to look further afield.

 

[Treestalker]

Copper would probably work, too.

One of the Civil War cannons made in England (Whitworth, IIRC) could go from breech-loader to muzzleloader by just running in the breech block. There was a disc of copper used at the interface between the barrel and the breech block to seal against gas leakage. Evidently copper was sufficient in strength to withstand battle loads in a rifled piece (it probably burned out quickly). I would make a washer/disc out of copper and try that before changing anything else on the gun, and go from there. If it doesn't work, then taking another turn on the plug (or a new plug) might be called for. As stated above, don't hurry, keep asking questions and try to resolve the issue without changing anything on the barrel itself. Good luck, Amigo.

 

[Scota@4570]

NM

 

[Flinty Scot]

If you try the washer, look up a chart showing the galvanic potential between different metals.
The washer would need to be very close to the barrel composition on the chart to minimize the risk of hidden corrosion at the breech and at the plug's mechanical seal. (You may be able to learn the barrel metal specifics.)

Discussing the issue with the manufacturer may help with your options - if liability doesn't get in the way.
I hope this helps.
https://www.engineeringclicks.com/galvanic-series/