Case Hardened Breech Plugs

[Roger B]

Hi, all!
 I recently had a discussion with a highly experienced maker about a Hawken breech plug that I had engraved and color case hardened on a rifle that I had been shooting.  I'm now in the midst of a rebarrel on this gun because I was only able to make it shoot a single good group over the past 5 years.  At any rate, the maker suggested that the case hardened threads on the plug probably needed to be annealed for safety.  That makes perfect sense, though I had never thought about it before.  I've seen original guns, both rifles and smoothbores, with case hardened plugs and wondered if they had their threads annealed.  Just thought that it might be a interesting subject to discuss.
Roger B.

[sydney]

Hi--What type of steel is the plug make from??
       Sydney

[B.Habermehl]

Origional guns were made from wroght iron, case hardening probably made the material some what stronger in the same way Maus... Actions were. Modern castings with un known alloys in them. I don't know.  BJH

[jerrywh]

 Most case hardening is no thicker then .010 maximum. I can't see where that would be a problem.

[rich pierce]

Only a problem if it’s hardenable steel.

[T*O*F]

Almost all long range rifles have color case hardened breechplugs and with heavy bullets they are subjected to more stress than your common ML.

A common trick when hardening breechplugs is to screw a large nut on the threads.  It acts like a heat sink during the quench

[David Rase]

Roger,
When I case harden a breech plug my normal process is to thread a nut over the threads.  As Jerry stated above, case hardening is only about .010" deep so the nut protects the threads.  I also temper all my case color hardened parts at 400 degrees for an hour in my shop toaster oven.
David

[Roger B]

I don't really know what type of steel it is.  It came installed on a Bill Large marked barrel, and appears to be hand made as opposed to cast.  TOF and David; I really appreciate the tip about putting a nut on the breach threads. It never ceases to amaze me what I learn from this site.  Thanks, guys.
Roger B.

[greybeard]

If you wash the threads with a strong copper sulfate solution the threads will not be case hardened.
  According to John Bivens.        Bob

[Jim Kibler]

Yes, copper plating is commonly used to create a barrier for carbon migration.  I'm familiar with people using a typical plating process, however the copper sulfate process sounds interesting.  You can also buy commercial comounds that can be painted on the surface to prevent carburizing.  For industrial processes, I believe I've seen ceramic caps being used to cover threads as well.

Jim

[rich pierce]

They mighta used clay, back in the day.

[Bob Roller]

Hi, all!
 I recently had a discussion with a highly experienced maker about a Hawken breech plug that I had engraved and color case hardened on a rifle that I had been shooting.  I'm now in the midst of a rebarrel on this gun because I was only able to make it shoot a single good group over the past 5 years.  At any rate, the maker suggested that the case hardened threads on the plug probably needed to be annealed for safety.  That makes perfect sense, though I had never thought about it before.  I've seen original guns, both rifles and smoothbores, with case hardened plugs and wondered if they had their threads annealed.  Just thought that it might be a interesting subject to discuss.
Roger B.

I finished a .451 long rang rifle for myself in 2003 and sent the tang and plug to a company in Ohio
and the man that did the work told he had put a sleeve over the threads to keep them from hardening.
That .451 would generate higher pressures on ignition than the round ball Hawken.

Bob Roller

[Roger B]

Bob;
I was hoping that you would check in!  What type of steel do you think Bill used to make the breach plug?
Roger B.

[Bob Roller]

I don't really know what type of steel it is.  It came installed on a Bill Large marked barrel, and appears to be hand made as opposed to cast.  TOF and David; I really appreciate the tip about putting a nut on the breach threads. It never ceases to amaze me what I learn from this site.  Thanks, guys.
Roger B.

Depending on when it was made,that Bill Large barrel could be 1144 "Stressproof"
or if later,some sort of leaded steel called "Tellurium"That may be what we call
12L14 now.Maybe a metallurgist can say what it is. I do know from years of using
1144 "Stressproof" for lock tumblers that if case hardened it can be brittle as glass
and I learned this when I case hardened a tumbler made from it was dropped on a wooden floor
and it broke.I can't time frame this use in Bill's shop and I don't think old invoices
from steel companies still exist from his shop.The only way I know to tell without
a professional analysis would be to cut 1/8 off the muzzle and heat it read hot and
quench in water. If if gets hard,it's probably 1144 and if not the it's leaded steel of
some kind.The reason Bill quit the 1144 was because he got a bad bar with a hard place in
it that destroyed an expensive long deep hole drill and the steel company refused to make
it good.I took the bar with the broken drill point and made tumblers out of it until I got
to the broken drill. I took it back to Bill and he made up a new long drill.As I recall,it was
a .32 caliber and the carbide tip was still good but when it hit the had place it wound it up like a corkscrew.
Those drills were hollow and carried about 600PSI oil pressure.

Bob Roller

[Roger B]

Thanks, Bob! Doubt that it was 1144, as I am still handsome and have both eyes!
Roger

[Dphariss]

Hi, all!
 I recently had a discussion with a highly experienced maker about a Hawken breech plug that I had engraved and color case hardened on a rifle that I had been shooting.  I'm now in the midst of a rebarrel on this gun because I was only able to make it shoot a single good group over the past 5 years.  At any rate, the maker suggested that the case hardened threads on the plug probably needed to be annealed for safety.  That makes perfect sense, though I had never thought about it before.  I've seen original guns, both rifles and smoothbores, with case hardened plugs and wondered if they had their threads annealed.  Just thought that it might be a interesting subject to discuss.
Roger B.

If its MILD steel or 8620 ( a steel designed for casehardening)  then it needs only a mild heat treat an hour of so at 370 degrees.
If its 4140 or other steel with more than 20 maybe 30 points of carbon then one MUST know the temperature it was quenched at. 4140 can be safely casehardened but if quenched at critical temp for 4140 it will TROUGH HARDEN and needs a higher temp anneal which will effect the colors or it will BREAK in all likelihood.
Even mild steel may through harden in thin sections like the thread corners or points of if a lockplate or other long part needs to be straightened a slight anneal reduces the possibility of the case surface cracking. Thus the 370 degree soak. It tempers the steel and takes away some of the brittleness.
So make breeches of 1018 or use castings of 8620 or professionally casehardened by someone who KNOWS how to deal with the actual alloy.
1018 was used for this and Keith Kilby at Wyoming Armory did the hardening in colors. He anneals to 370 after the quench. Photo does not do justice.

Dan


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[Roger B]

Wyoming Armory was where my breech was done.
Roger B.