Coned breech plug face PC?

[red owl]

Some replicas such as CVA have a coned face on the breech plug. If you want to scrap fouling you need a rounded tip on the scraper to match the contour of this cone.
   Is this a historically correct feature?
   Why was it done? I've thought about it and wonder if the cone prevented a "dry ball" from being rammed right up to the breech plug.  A shooter could dribble a few grains of powder into the cone area and shoot out the ball.
   Any insight would be interesting.

[smallpatch]

Can't think of any reason a craftsman would go through the extra effort to cone a breech plug.
Flat would be natural, as you would file it that way when fitting.


In fact, a cone, or dish would just let a dry ball get that much further back over the touch hole . 
I assume we are talking flint locks?
I have coned a couple myself, just to get locks to line up properly.  Today's barrels have WAY longer breech plugs than originals, so it's sometimes necessary.
Of course, there are the Nocks and patent breeches, which are designed to help ignition...... Another story all together.

[Joe S]

Dishing the face of the breech plug will give you higher muzzle velocity.  On the .50 caliber barrel I tested, the increase was about 75 FPS.

[smallpatch]

I'd like to see the data on that.  Hard to imagine that a .030 or .040 dish on a breechplug would consistently cause a 75 fps increase.
I guess it's possible. 
I think we're getting away from the OPs question.  Was it PC?

Tough job with hand tools, but I guess an industrialized shop could have built them.  All speculation of course.

[hudson]

The recess in the CVA breachplugs I am familiar with are 1/4 in. diameter depth a wild guess 5/8 in. The problem with this system is fouling from cleaning will case misfires. The cross drilled from the drum is at the vary bottom. I was told this breach design was a safety feature as the drum goes through the barrel and into the breach plug. I have noticed higher velocity from my CVA fifty than a similar Green Mountain Barrel. This could be from the different rifling.

[JTR]

Well, no one else has answered, so I'll give it a try.

I've had at least 20 breech plugs out of old original barrels, and I've never seen one that was coned. Some were corroded away on the face in a random way, but nothing that I would call purposely done that way.

Never say never, but in this case I'd say positively, not ever,,,, almost.
John

[Bob Roller]

I'd like to see the data on that.  Hard to imagine that a .030 or .040 dish on a breechplug would consistently cause a 75 fps increase.
I guess it's possible. 
I think we're getting away from the OPs question.  Was it PC?

Tough job with hand tools, but I guess an industrialized shop could have built them.  All speculation of course.

I THINK I recall reading about cupping the face of a breech plug in the old Buckskin Report and there was a measurable increase in velocity using the same powder charge when the plug was flat faced.I don't know about coning them. Seems to me Don King may have had something to do with this but it's been too many years to say for sure.A ball nose end mill was used.

Bob Roller

[Joe S.]

shaped charges,ect which are coned produce a measurable increase in destructive power vs. standard explosives.In theory why wouldn't the same be true of a muzzleloader?

[Dphariss]

I'd like to see the data on that.  Hard to imagine that a .030 or .040 dish on a breechplug would consistently cause a 75 fps increase.
I guess it's possible. 
I think we're getting away from the OPs question.  Was it PC?

Tough job with hand tools, but I guess an industrialized shop could have built them.  All speculation of course.

I THINK I recall reading about cupping the face of a breech plug in the old Buckskin Report and there was a measurable increase in velocity using the same powder charge when the plug was flat faced.I don't know about coning them. Seems to me Don King may have had something to do with this but it's been too many years to say for sure.A ball nose end mill was used.

Bob Roller

Don used to cup breeches and testing by one of our Guild members shows it does increase velocity. This be posted the data here but could be wrong.

Dan

[Dphariss]

I'd like to see the data on that.  Hard to imagine that a .030 or .040 dish on a breechplug would consistently cause a 75 fps increase.
I guess it's possible. 
I think we're getting away from the OPs question.  Was it PC?

Tough job with hand tools, but I guess an industrialized shop could have built them.  All speculation of course.

Dish is deeper than that. If I use a 1/2" ball end mill I make them about .240-.250 deep. As did Don King.
PC?
The Nock Breech dates to the 1780s. There were other breech designs as well. But few if any Americans did the testing and research to show that there was any advantage. The better percussion patent breeches were generally cupped.
Me I really don't care if its PC or not. I am not making guns in 1770 and I don't pretend to be. I don't make everything out of wrought iron. I don't get locks from Europe. Nor do I use 20 c. plastic stock finishes. Something that is common even with people that can't stand vent liners  This is more noticeable than a cupped breech face. I make guns in the style of the past to suit Dan. If it suits me its not likely to outrage anyone, unless they are vent liner snobs 
BTW the same tool used to make a mould cavity will cup a breech for the bore size. So the ability was there. But I doubt they did it.
Dan

[Joe S]

Red Owl - Is a dished plug PC?  I certainly don’t know.  But, it’s free velocity and can’t be seen.  

smallpatch - Ask and ye shall receive.  Got home found the data.  I said the difference was 75 FPS.  It’s was actually 87 FPS.  OK.  So I lied. Disclaimer – I’m old, and getting stupider by the day.

Experiment Conditions:

38” .50 caliber barrel (Getz)
70 grains Goex FF
Coned flash hole
0.062” flash hole diameter
15’ from muzzle to chronograph
Spit lubed 0.018” pillow ticking patch
0.495” Hornady ball
Ambient Temperature 80 – 90 degrees F
Flat faced breech plug
Breech plug face dished in hemispherical shape with 1/2“ ball end mill.
Sample Size – 15 for each breech plug


Table 1
Breech Plug Face Shape Experiment – Units are feet/second



Two-tailed T-test: T= 8.393291 The P-Value is < 0.00001

You’ll have to ask Dan how deep he dished the face of the breech plug.




Note:  I am the real Joe S – whoever is posting as Joe S. is an imposter.  If anybody cares.

This is what I look like:



I don't know what that other guy looks like.

[smallpatch]

Joe S,

From your data, it certainly appears to help.  Seems to be a few more variables, but the data sure points that way.
Wow, who knew. 
Thanks so much.

[oldtravler61]

Nice pic Joe. Always smiling!

[Joe S]

smallpatch - I agree that there are more variables.  The fundamental principal seems to be unequivocal – dishing the breech plug face will result in significantly increased velocity.  Exactly how much velocity may depend on the individual barrel, caliber, load, patch / ball combination, possibly lube, etc.  When I get some time, I intend to explore some of these variables in more depth.  But, we are off topic, and if we’re not careful a moderator is gonna bust our chops.

Keep on truckin' !

[Daryl]

The breech plug I removed from a single barrel Blissett 12 bore, has a coned 'patent' breech plug face. The cone, which actually has a bore sized entrance gave access of the main charge to the nipple flash channel which was shortened, due to the cone.
Of course this is a different scenario than possible coned flint plain flint breeches.

[Joe S.]

Not an imposter,but a Joe S. also quess I will have to work on a different handle,sorry.My beard is not as long and not as grey as yours,I have way more hair on my head though.For sure I have been called a cartoon character,more than once  .For now it looks easy to tell us apart, I don't know a damm thing about muzzleloaders other than dumping powder down the barrel,ramming a ball home and praying it goes boom.

[red owl]

Well, let me restate things and get back on topic.  As I understand everybody a coned breech plug is pc but it is rare and seen mostly on British firearms and maybe a few shotguns. On a rifle the coned breech plug is seen on the patent types but seldom where the drum is used.
   And.....I have been sort of drifting ever more towards pc "ness".  My thinking is that the whole deal is shooting firearms that "once were" so if we reproduce them- might as well copy the originals as much as possible.

[Joe S]

You sure know how to get an argument started Red Owl.  These boys can burn a lot of oxygen on this topic.

Most of the folks here go to an awful lot of trouble to build historically correct guns, down to the finest detail that they can manage.  It seems to me that there are only three areas where you will commonly see intentional deviations:

1.   Screw-in coned vent liners on guns that probably didn’t ever have them
2.   Aniline dyes
3.   Modern plastic finishes

Of course, most of us can’t make wrought iron barrels and locks as well.  Other than that, Dan makes guns that suit Dan, and Joe makes guns that suit Joe.  Our styles and tastes are not identical.

Regarding this topic, I suppose some folks who think that an extra +100 FPS or so will help them out will start dishing the faces of their breech plugs.  Most people probably won’t.

[Jerry V Lape]

Joe S. (the other one):   Shaped charges are something I do know about.  They do not create more explosive power.  Rather they focus the blast like a magnifying glass focuses light to a designed focal length for the purpose of creating a jet of superheated gas/flame on a small area enabling the jet to penetrate deeper into the targeted material.  If you had a shape charge in a muzzleloader it would most likely  melt a hole through the ball and rip it to shreds and molten lead rather than increase it's velocity. 

[hammer]

I recall reading that different breech plug faces were claimed to reduce recoil.  That was back in the 19th century when gunmakers were in hot competition in England and internal and external ballistics were in there infancy.  Later trials showed no difference in recoil.
I suspect the proven, slight increase in velocity here is due to a more efficient burn of the main charge with the dished face.   

[Joe S.]

Joe S. (the other one):   Shaped charges are something I do know about.  They do not create more explosive power.  Rather they focus the blast like a magnifying glass focuses light to a designed focal length for the purpose of creating a jet of superheated gas/flame on a small area enabling the jet to penetrate deeper into the targeted material.  If you had a shape charge in a muzzleloader it would most likely  melt a hole through the ball and rip it to shreds and molten lead rather than increase it's velocity. 

perhaps I phrased my thoughts wrong.If we are putting a cone at the end of the breach we are in theory focusing the blast to some extent. Not really a shaped charge per say like you would see in an RPG.How else would you explain the increase in velocity?

[Keithbatt]

Joe S. (the other one):   Shaped charges are something I do know about.  They do not create more explosive power.  Rather they focus the blast like a magnifying glass focuses light to a designed focal length for the purpose of creating a jet of superheated gas/flame on a small area enabling the jet to penetrate deeper into the targeted material.  If you had a shape charge in a muzzleloader it would most likely  melt a hole through the ball and rip it to shreds and molten lead rather than increase it's velocity.  

perhaps I phrased my thoughts wrong.If we are putting a cone at the end of the breach we are in theory focusing the blast to some extent. Not really a shaped charge per say like you would see in an RPG.How else would you explain the increase in velocity?

Here is my attempt at explaining it:

Upon ignition, propagation of the flame front through confined black powder is rapid, but not near detonation velocity, and not the velocity where a "shaped charge" effect is present.  The shaped charged effect is known as the Monroe effect and is focusing a blast wave via hollowing out the FRONT of a charge, allowing the expanding gases from a high explosive charge to reflect against one another and direct much of the explosive force in one direction.

The coning or rounding of the back of a charge of black powder does not affect the charge in this way.  So what does it do?  My best guess is that as the powder turns to gas and solids (2 KNO3 + S + 3 C -> K2S + N2 + 3CO2), the combustion products want to go outward.  The only way out is out the muzzle, but the gases need to figure out where to go.  On a macro scale, they all go forward, but imagine what's happening at the breech face.  The powder near the middle of the breech face wants to go outwards, towards the exterior walls of the barrel, and it does.  With a flat breech face, it hits a 90 degree wall and is forced to make the turn forward.  Now picture the rounded or coned breech face.  The powder makes a gradual smooth transition from outward (normal to the bore), to parallel to the bore.  

It's my belief that the rounded breech contributes to a higher efficiency in combustion product flow and consequently results in increased velocity.

Keith

[Daryl]

I can see this as the powder gasses that travel backwards and hitting a flat breech, are then, for the most part, directed outwards at 90 degrees to the sides of the chamber, not back into the powder chamber where the conflagration is taking place and/or must turn 180 degrees to reverse back into the 'chamber or powder area'.

The powder gasses that hit the coned or rounded breech face are deflected back into chamber or burning powder more quickly (not out at 90 degrees or reversing 180 degrees - thus more of it is directed back into the burning powder to increase combustion temperatures. This will or should more effectively help burn the charge that is there in combustion.  With the cone, there is none of the 90 degree bouncing of the flame front, but more or all of it is redirected back into the powder chamber to exacerbate combustion.  This in itself would make the charge more efficient, thus increasing velocity at the rate of the increased efficiency.

Thus, with a flat breech, less powder gasses are returned to the charge than with a coned or cupped breech face. Makes sense.

Too, it stands to reason this should also reduce the amount of solid deposits in the bore (perhaps noticeable, perhaps not), due to the better combustion and higher flame temperature.

[Jerry V Lape]

There is a possibly simpler explanation.  Increased velocity indicates one of two things happening.  Either pressure is increased in general or pressure is maintained a little higher further down the  bore. The later would in smokeless powder parlance be "more progressive".  We would have to know the pressure/time curve for the powder burn  with the different breech configurations to achieve a more intelligent guess as to why the coned breech appears to be producing a little higher velocity.  This assumes all other variables are held constant which is tough to determine.  For example the way the patching arranges itself at the rim of the cone may be the real difference - somehow sealing itself a little better with the cone than the straight breech. 

[Joe S]

The test barrel originally had a flat faced breech plug installed, and the flash hole drilled.  The depth of the dished face is only about ¼”.  Thus the ball (and patch) lie well forward of the flash hole and the dished face, so the patch is not sealing anywhere near the cone.

It is not immediately obvious to me why the burn rate or pressure curve characteristics of the powder should be different with a dished face.  A dished face will focus pressure waves in the same manner that a parabolic mirror focuses light waves.  If the focal point in in the right place, the ball will experience higher forces, and hence increased velocity, without a requisite concomitant change in chamber pressure.   I suspect the causes of this phenomenal lie in that direction.

But, we are speculating on questions that we don’t have the tools to answer.  This would make an interesting PhD thesis for someone.  Not me.  I'm too old.