making a breech plug

[hitandmissengine]

Upon inspection of the breech plug from my 40 cal. Long rifle I found it to be in need of replacement. It is one of the patend breech design. The plug is scared very bad on the powder end. The lenth of said plug threaded boss is about .375 inch now and would be around .340 upon filing and smoothing powder end surface. From what I have read this is to short for thread boss. From what I have gatherd the treads must be at least 1/2 inch in lenth. I dont see a plug on internet availabe for replacement. Being a retired machinist I think I could make one. Probably of the drum type due to easy drilling of flash hole. Question is what type of material to use for plug. I know that modern powders reach very high pressures and require heat treated and hardend steel. Given this project is for black powder I would think that pressure will be much lower. With that said can anyone tell me what type of steel to use. Must said plug be hardend after machining . Is standard 1013 or even 4140 ok fkr use.
Thanks for any help

 

[Flint311]

From reading on this, it was common to use a standard bolt and cut off what's needed. Then weld or solder the tang on. Flatten, file, polish the face first and get square.

Just my $.02 worth.... (and usually people get change :redface: )

But for a patent breach, not sure how to add on. As a machinist, maybe you'd have an answer? Let us know how you do it! :thumbsup:

 

[davec2]

I have made many breech plugs out of 12L14 free machining. Plenty strong for a black powder breech and very easy to machine. Actually, you can use just about any mild steel or the 4130 / 4140 alloys as well. I often use whatever I have on hand. No need to harden or heat treat at all.

 

[44-henry]

I have made several from plain old 1018, but 12L14 is as was entioned is much nicer machining steel and is often what muzzleloading barrels are made from.

I doubt a properly fitted and designed plug .375 or even a bit shorter would prove unsafe, many originals were much shorter, but since it is a patent breech there is nothing stopping you from making it longer and that would be wise, but there are other variables to consider such as diameter and thread pitch.

 

[Grenadier1758]

I know that modern powders reach very high pressures and require heat treated and hardend steel. Given this project is for black powder I would think that pressure will be much lower. With that said can anyone tell me what type of steel to use. Must said plug be hardend after machining . Is standard 1013 or even 4140 ok fkr use.
Thanks for any help

Modern black powder is still black powder. Even the pressures from the synthetic powders that are used as substitutes for black powder could be safely handled by the 3/8" threaded breech. Since you are planning to use only black powder or black powder substitutes, you should be safe.

You don't want to harden the breech plug. You want the metal to be able to absorb the shock of firing.

 

[Tinker2]

Looks like all good advice to me.




good luck
William Alexander

 

[Zonie]

There is no "1/2 inch length" rule although many of the modern breech plugs meet or exceed this amount.

Generally speaking the length of the threaded portion should be somewhere between .6 and .9 times the thread diameter.
If the thread size on your .40 is 1/2 inch, the .375 length would be in this ballpark.

After reaching a length of 1 times the thread diameter, further increases in length serves no purpose as far as strength goes.

Muzzleloading guns barrels are often made from 1018, 1020 or 12L14.
All of these are in the 55-65 ksi tensile/30-55 ksi yield strength area.
It is best to use a hot rolled material because of its greater elongation properties.

No heat treatment for these materials is possible (except for stress relief), or needed.

 

[galamb]

I have a muzzle loading builders book published back in the 1960's - long before you could buy on-line at Track of the Wolf etc.

In the section on breeching the barrel it suggests that you go to the hardware store, obtain a fine threaded 5/8" bolt, bottom it out in your breech - cut it off to the desired length and file the top flat so that you can weld a piece of flat steel to fashion the tang.

And it just says "a bolt" - doesn't even specify grade 5 or 8

As Zonie notes, just about any of the screw steels would be fine. A breech plug is just not as complicated as some would have you believe.

 

[hitandmissengine]

Are breech plugs made of same materials as barrel?

 

[Zonie]

Yes.

If you make the breech plug out of some material that's stronger than the barrel material, that's fine but going out of your way to find material that is much stronger isn't worth the time spent doing it.

 

[coloradoclyde]

How are patent breech plugs like a nock's or a T/C made?

 

[Zonie]

TC and other "patent breech plugs" are usually steel investment castings.

I don't know what the type of steel used is and there are a lot of different steels that can be cast.

The simple, castable, carbon steels have strength properties similar to low carbon wrought steel.

 

[coloradoclyde]

It makes me wonder if what the OP thinks is an eroded breech plug is simply an unfinished casting ...?

I can remember inspecting one that I thought was heavily pitted and it just turned out to be unfinished cast metal...

I have never seen a breech plug that was in such a bad condition as to need replacement where the rest of the barrel did not... :idunno:

 

[hitandmissengine]

Thanks Zonie. I checked the major diamiter of the plug threadsand it came out to .648. That by .6 puts the thread lenth around .390. If i file the plug down to a good smooth surface the lenth will be aprox. ?340. I think that I will make a steal spacer to fill any gap between plug head and barrel bore. Then screw the refinished original breech plug down down on the spacer. Hpefully that will well fix the problem.
Thanks

 

[hitandmissengine]

It my be unfinished or for that matter poorly finished. The rifle was a kit project for another owner. There are other poorly worked areas on other metal parts of rifle. All in all, the original owner seems to have tried to do a good job.

 

[ohio ramrod]

I make many breech plugs from stress proof but that is just what I have. As stated most common steels are strong enough 12l14 is probably the easiest to machine especially if you have a lot of hand hacksawing and filing for the tang. :idunno:

 

[Grenadier1758]

Thanks Zonie. I checked the major diamiter of the plug threadsand it came out to .648. That by .6 puts the thread lenth around .390. If i file the plug down to a good smooth surface the lenth will be aprox. ?340. I think that I will make a steal spacer to fill any gap between plug head and barrel bore. Then screw the refinished original breech plug down down on the spacer. Hopefully that will well fix the problem.
Thanks

Perhaps your best bet would be a lead washer sized to crush as you seat the breech plug into the barrel. That will fill the gap and hopefully simplify the making of the sizing washer.

 

[hitandmissengine]

Upon further inspection of plug I feel it is best to replace it. The plug is of the patent breech design. Machined with 11/16-20 threads. I see no real problem in duplicating the plug with exception of nipple flash hole. I beleave that once I machine the new plug I can drill a flash hole channel. The channel will be drilled from lock side of plug, threw nipple cavity and then straight into the patent chamber. Once cannel is drilled I will
Thead the channel where drilling began on plug. Then seal it with a screw. The original plug was a casting and required no screw to seal the channel. Seems like all should work ok, but remember, I am new to muzzle loading. Any advice will be great.

 

[ZUG]

This breach plug was made out of 1018 cold rolled steel. As a former machinist you should be able to do the same :v

 

[hitandmissengine]

Thank you zug. Great example and layout. Is the breech cuped at the face? Or, is it a patent type with powder resovoir machined down into the plug? How are flash vents (channels) drilled to connect nipple drum to powder resovoir.
Again, thanks for the help.