chambered breech

[Pukka Bundook]

Rich,

Ignition of the common breech  used to be described as "Igniting one corner of the charge".
Whereas with the chambered or Nock's type, the somewhat  confined powder of the anti-chamber ignites and sends the spurt of flame  throughout the main charge, more or less igniting it all in one go.  (That's the theory at any rate.)  It's all rather academic.

In a way, this is  what was done with (Pardon me for saying this here)  the  first .303 black powder cartridge;   The powder was compressed into a single pellet with a hole through the centre, so the primer flame  ignited it "all at once".    (Now, please forget I wrote this!  :-)

Best regards,
Richard.

[smart dog]

Hi Rich,
The purpose of the chambered breech is exactly as Richard describes very nicely above, to make the charge of powder work more efficiently and get maximum force for a given charge.  It was not to speed initial ignition from the pan.  If you look at old drawings of these breeches (shown below chambered breech on left, Nock's on right) or Nock's advertising for his breech, you can see that the standard chambered breech likely would slow down initial ignition because the vent hole was longer having to go through barrel wall and breech plug to reach the smaller powder chamber than it would if it was drilled into the bore of the gun as it would with a flat breech plug.


With a flat plug, the total charge is lit by a weak jet of heat at its end and has to burn through the stack of powder a little like lighting a fuse at one end.  That of course is an exaggeration because in the confined space of the barrel, the accumulation of hot gases as powder burns will cause the burning of remaining powder to accelerate unlike a fuse in open air.  In contrast, a strong jet of powder fueled gases from an antechamber or small powder chamber would speed up the burning of the main powder charge.  One advantage for the chambered breech described at the time is that it allowed use of shorter barrels because there was no need to confine a bullet or shot load in a long barrel to take advantage of the full force of a slow burning charge of powder.  Nock added the horizontal antechamber to allow the charge in the chamber to be closer to the pan much like coning the inside of a vent liner so initial ignition was fast.  I suspect that the secondary ignition of the main charge was so fast as to be imperceptible and that the time from pan flash to bullet exiting the barrel was faster for a given barrel length than when using a simple flat breech plug.  I also suspect that replacing the longer vent hole in a chambered breech with a coned liner will solve any slow initial ignition problems and make Nock's design unnecessary. 

dave

[L. Akers]

The chambered breechplugs I have made all have the chamber made with a 1/2" glass-drilling scrape bit. The diameter of the hole extending into the octagon portion from the base of the chamber in a Manton-style breech is 1/3 the bore diameter.  In a Nock style breech the diameter of the hole between the base of the chamber and the antechamber is 1/10" to no larger than 1/8" and 3/32-1/8" in length.  My ante chambers in the Nock breeches are the diameter of the liner tap drill.  Manton breeches (Manton's work-around Nock's patent) were usually inset so the lock sat closer to the charge reducing the "fuse length".  Both these breeches work by sending a jet of flame under pressure through the center of the charge ignighting more powder at once. 

Loading procedures have to be modified when using one of these breeches to insure positive ignition.  It has been noted that when dumping the powder it may not enter the small communicating chambers.  Trickel the first couple of grains of powder before dumping the remaining main portion of the charge.  The smaller volume of powder will enter the smaller holes easily and ignition will be sure.  It only takes 2-3 seconds longer to do it this way and soon becomes habit.

[Joe S]

Some years ago, Dan Pharis made patent breeches for Larry Pletcher to test.  The tests measured ignition time of various chamber types.  According to Dan, Pletcher found that Nock’s breech was not the fastest, but it was the most consistent.  I have perused Pletcher’s publications, but I did not find that particular test.  Without a statistical analysis of the data, I would be cautious about drawing any conclusions.

A chronograph and a couple of hours at the shooting range could shed a lot of light on the questions posed in this thread.

[Bob Roller]

The late T.K. (Tom)Dawson had a Manton 16 bore short deer stalking rifle
with this Nock type breech and it went off like a centerfire.I think he used DuPont
or maybe Curtis &Harvey powder.

Bob Roller

[Pukka Bundook]

All the above very interesting.

Jose,
I suppose a good lock was required as well, but if the same one was used in all the tests, actual times would remain in order.

Please forgive my wandering mind;

I Wonder, if the faster ignition we see with a matchlock is because of the somewhat different pan shape often encountered? 
The latter's pans are often a bit deeper and rather small;
Do you think that on ignition, the flash is thrown back on itself,  rebounding as it were,  from the 'wall' opposite the touchhole, and Into the touchhole?

If this is too OT please disregard....but it has me wonderin'!

[smart dog]

Hi Richard,
Interesting question.  It may be as simple as a 3/8"-1/2" diameter match burning on its end ignites a lot more powder simultaneously then sparks from a frizzen.  Also a wide shallow pan presents a "tray" of powder to the igniter enhanced by access to oxygen in the air.  A deep, narrow pan might be more like a cannon fuse because it has to burn from the top down.

dave

[Kevin Houlihan]

Perfect timing for this topic...
  I’m building a pistol now with a chambered breech.  No “anti-chamber”, just a long breech plug bored with a 5/16” endmill. This kind of resembles figure 31 in the pic by Smart Dog but without the anti-chamber.  This will allow me to place the lock closer to the end of the barrel.  My question is about drilling the touchhole liner.  I’m using a White Lightening liner.  Do I screw in the breech plug and then just drill and tap the liner just as you would normally do? Or… do I install the liner only into the barrel, flush it with the breech threads and then install the plug, and if so how large a hole do I drill in the wall of the plug to connect the chamber to the liner?    Thanks.
Kevin

[rich pierce]

So, based on additional input above I am still not buying it gives faster initial ignition. It may give more efficient burn and thus velocity. The ball may likely exit sooner. Maybe this is semantics. I’ve never used a patent breech in a flint gun. It might be appropriate for a high end flint Plains rifle but I’m not sure it was used much in America on flint arms.

[Joe S]

Pukka

I Wonder, if the faster ignition we see with a matchlock is because of the somewhat different pan shape often encountered? 

At the risk of Dennis getting after us for digressing, I will answer your question with two caveats:

1.   I dislike speculating about things that can be measured. The reason is that either you know the answer, or you’re guessing.  I have measured the accuracy of speculation several times, and so have many other people.  The answer is always the same: there is no such thing as an “educated opinion” or an “educated guess”.  If you don’t know, you’re guessing, and if you’re guessing, you may as well ask your dog.  People do not like to hear this, and they generally don’t believe it, but that’s how it is.

2.   According to Larry Pletcher’s data, “…..our eyes and ears are terrible tools for judging flint events.”

So, regarding your question: I have heard it said that matchlock’s ignition is faster than a flintlock’s ignition, but I have not seen any data that would support or refute that observation.

Then, to rephrase your question – do we have any reason to think that pan shape might affect ignition time?  The closest thing that I know of is Pletcher’s tests on different priming powder configurations in the flash pan – close to the vent, away from the vent, covering the vent and so forth. The only statistically significant effect Pletecher measured was that with the powder away from the vent, ignition was slowed by an average of 0.007 seconds.

So, to the extent that this experiment can serve as a proxy for different pan shapes, the answer is no, we don’t have any a priori reason to think that pan shape influences ignition time.  But, we would have to measure it to be sure.

Fat Joe

[bgf]

I have this kind of breech on my chunk gun (flint), actually on two different barrels.  With coned liner and edges of chamber rolled and polished, ignition is quite snappy and fouling is rare.  In fact the touchholes seem to stay clearer than on a flat breeched gun when wiping between shots.  I imagine the fouling gets stuck at the chamber mouth and not squished into the touch hole.  I never wipe the powder chamber.

Thanks to a hooked breech, I can easily clean in a bucket of water, and the breeches are always spotless when I bother to check them.  I'm a big fan of these breeches and will likely use them on most future builds.  I have seen a few original American Longrifles with that setup, but most were probably done that way during a conversion to percussion or possibly to avoid shortening a barrel...

So, I wouldn't say they're better, but I don't think they are inferior in any way.

[Pukka Bundook]

Joe,

OK I'll go and stand in a corner.  Let me know when I can come out won't you?  :-)

Very sorry.  I Presumed (and I know you don't like that!) that Some matchlocks were faster than most flintlocks, as they always "appear" to be.   Again, very sorry!
Until we do some proper testes, I will in future keep my mouth shut and hand off the keyboard.  Do we have  a deal?

All the very best,

Richard.

[smart dog]

Hi Richard,
Don't worry and keep posting your thoughts.  The human world runs on "educated opinions" and "educated guesses" and if it had to rely on the slow process of scientifically testing every idea or action it would come to a standstill. None of the testing by Larry P.  has any bearing on the effect of pan shape on ignition (I am familiar with all the work published in Blackpowder Mag) so Jose was "speculating" beyond the data.  I have been a practicing scientist and trained statistician with more than 30 years experience applying science to guide policy, speculation and hypotheses are good things as long as we all recognize that they are just ideas until tested with data.  Jose is correct that our senses often deceive us and that is ironically because they are connected to our brains. They are not "mindless" instruments measuring the world but "mindful" instruments that are constantly influenced by the preconceived notions imbedded in our brains.  Anyway, one does not need to resort to a "bully" pulpit to make that point.   

dave

[Joe S]

Sorry Pukka - I didn't mean to sound so pontifical. 

We could know the answer to Dave's question fairly easily, because all that is required is a gun with chambered breech, a couple of bolts with the appropriate thread and a chronograph.  Have the face of one bolt shaped into a hemisphere with a ball end mill, and the other bolt will be a flat faced breech plug that will serve a a control.

You can now determine whether the increase in velocity from a chambered breech plug is due solely to the hemispherical shape of the chamber, or to some other feature. It would be especially nice to test Nock's breech, and compare to other chambered breech designs as well.

Shoot 15 shots with each breech plug, using the same load of course, and then we will know something.  I would be happy to do the test myself if I had a chambered breech, but I don't.

Here is my test rig:



Dave

Jose is correct that our senses often deceive us and that is ironically because they are connected to our brains.

“…..our eyes and ears are terrible tools for judging flint events.”

This a quote from Larry Pletcher, not my observation.

[bob in the woods]

Faster ignition ?  I don't buy it. Even if true, is it worth it in terms of use in the woods ?   Yes I know that there are some who remove the barrels of their rifles and clean by pumping water through them. That works well, however I live in the woods and use / carry my gun almost every day. The flat breach works extremely well, and the barrel is very easy to clean and otherwise maintain without having to worry about a smaller breach chamber and separate tools. Extreme reliability along with ease of maintenance.
What's not to like ?

[Pukka Bundook]

OK Dave and Joe, but I will watch what I say as I see Joe's points as relevant.  :-)

I am tempted to make up some differnt styles of patent breech to try, but think I have enough half done projects at present.

Woods Bob,
Your reasoning is very sound, and that is why arms for defense were often made with the simplest of breeches.

For sportsmen shooting flying, the various attempts to produce faster and harder shooting guns lead to a variety of patents in the breeching up. 
Much discussion ensued, and on this page it still goes on.  :-)

Best,
Richard.

[Long John]

Dave,

There are a number of factors that are all competing with each other when one considers the thermo-chemical process of propellant ignition and combustion.  Much of what I have learned was obtained in connection with my engineering practice and much of that I cannot share.  Here is what I can share.

Black powder combustion is controlled by the generation and mobility of sulfur-monoxide, an unstable, combustion intermediate product gas that serves as the carrier of oxygen from nitrate to carbon.  The more energetic the ignition source the faster SO is generated and the faster the combustion reaction starts and proceeds.  So this would suggest that having an antechamber that holds a smaller charge of powder might facilitate a more rapid ignition of the rest of the charge.   However, the combustion reaction comes to an immediate halt when the SO and flame-front collides with the cold steel of the chamber.  This would suggest that the "ideal" chamber is a sphere because a sphere has the largest volume for a given surface area - reducing surface area reduces the quenching effect of the chamber wall and provides the maximum combustion rate. (This is why Jose got slightly higher velocities with a hemispherically shaped breech face - he reduced the surface area for the given powder volume.  His results would have been different with a larger charge or with 3Fg powder.)  Now you know while the center-fire rifle crowd is so agog over the "short magnums" wither their short-fat cases.

If you are going to make a chamber with an antechamber in the breechplug then make the whole thing as close to a hemisphere as possible to minimize the flame quenching of the large surface area that comes from the complicated interiors like the drawings above.  Large surface areas lead to lower combustion rates (therefore lower velocities) wider variations in combustion rates between shots, and more fouling. 

On my doublegun I made recessed breeches in the breech plugs.  The recess is 0.375" deep and 0.312 in diameter with a 45 degree chamfer on the opening.  The vent is made with a white-lightning bushing that threads into a hole that is equal in diameter to the ID of the vent bushing, about 0.100" if I remember correctly.  This gives the gun a sufficiently large piloting charge in contact with the vent yet is as close to a hemisphere as I can get.  Since the barrels have hooked breeches cleaning is not an issue.  I haven't finished the gun yet so I can't tell you if it shoots.

Best Regards,

JMC
John Cholin
 

[Long John]

Friends,

I have a correction to my post.  I checked my drawings and the ante chamber in the breeches of my double gun is 0.250" deep, not 0.375" as my earlier post states.  This makes it closer to a hemisphere.  I think everything else is right.

Best Regards,

JMC
John Cholin

[Steve-In]

Was not one of the reasons for the patent breech so double barrels could be slimed down?  Here is an example from a fine dbl flint shotgun on Guns Int.  With a smaller chamber the locks can be set into a recess at the breech and still have a decent wall thickness.  The third and last photos show what I mean.

http://www.gunsinternational.com/guns-for-sale-online/shotguns/antique-shotguns-flintlock/william-young-bury-st-edmunds-s-folk-exceptional-19-bore-double-barreled-flintlock-sporting-gun-ca-1815.cfm?gun_id=100916800

[rich pierce]

Excellent point!

[Daryl]

Same here on these 3 samples. Original Manton, a small 20 bore by Cody and Taylor's 12 bore.  All have recessed breech sides, by far, though larger
cut-touts on the Manton.

[Bob Roller]

OK Dave and Joe, but I will watch what I say as I see Joe's points as relevant.  :-)

I am tempted to make up some differnt styles of patent breech to try, but think I have enough half done projects at present.

Woods Bob,
Your reasoning is very sound, and that is why arms for defense were often made with the simplest of breeches.

For sportsmen shooting flying, the various attempts to produce faster and harder shooting guns lead to a variety of patents in the breeching up. 
Much discussion ensued, and on this page it still goes on.  :-)

Best,
Richard.

"A wide variety of patents"? I saw a cartoon depicting the patent mania in England
and it was a man with a gun that went off in every conceivable direction and killed
every thing and everyone around it.It might have been in Robert Held's "The age of
Firearms". Maybe someone can post it for all to see.

Bob Roller