Not sure if this has been asked before, but what are your thoughts on the pressures generated in a muzzleloader like in comparison to the same load in a breech loader?
I would assume the same, but does it make any difference with the lack of a chamber, forcing cone, case head etc?

Also I seem to recall reading somewhere about an experiment where the chambers of a breech loader actually had slots cut in them from the breech to the end of the chamber. These were then fired without issue if memory serves me correctly. It may have been Burrard or Greener but I cannot find it. Can someone point me in the right direction?
Cheers,
GDU.

Greg: if that information is anywhere, it's probably here. Please let us know what you find.
Sporting Guns and Gunpowders: Comprising a Selection from Reports of Experiments, and Other Articles Published in the "Field" Newspaper, Relative to Firearms and Explosives, Volumes 1-2, 1897
https://books.google.com/books?id=inQCAAAAYAAJ

Given equal loads and equal charges of black powder, there is an immediate and obvious difference in pressures due to the gas loss that escapes from the flintlock vent or percussion nipple. In the case of flintlocks, the size of the vent is critical because going too large in order to get more reliable ignition also causes a corresponding reduction in chamber pressure that lowers velocity.

In a breech loader the inside of the case is normally a bit larger than the actual bore diameter thus more volume in the initial combustion area. Also the paper of the case & base wad would soak up some Heat, thus lowering pressure a bit. These may more than offset the loss through the vent. I have done a good bit of shooting with cap locks & with a properly constructed nipple never noticed much loss through it.

A former co-worker hunted with a .50 caliber "Hawken Type" caplock. First thing he would do when he had to replace the nipple was to drill it out to the point that when he fired it the hammer would be blown back to Full Cock. His idea was if a follow-up shot was needed he wanted to be able to reload as quickly as possible & not have to fool with re-cocking it.

Only way I know this could be determined for certain would be to run pressure tests on otherwise identical barrels with one set up as a ML'er & the other a breech loader. As I don't have the equipment to do this it is all purely speculation on my part. There are though factors which could point toward either.

Just the nature of firing a crimped cartridge with a bullet .001 to .002 larger than groove diameter is going to increase pressure over a similar load in a muzzleloader. No crimp to overcome or forcing of a larger bullet into the rifling with the front stuffer.

Since this is a shotgun forum & it wasn't stated otherwise I assumed we were speaking of shotguns & not rifles.

W W Greener spoke of turning some shotgun chambers quite this & them holding normal loads. When Julian S Hatcher was chief of Ordnance for the US Army he experimented with an ordinary 1903 Springfield in .30-06 by turning the chamber walls down to about .060" thick. These held the service loads but burst when fired with a proof load.

"Most" guns have some amount of safety factor built in, but its still not advisable to exceed what they were designed for.

Same physics apply, i.e. crimped shells and wads moving through a forcing cone vs neither in a muzzleloader. In fact, slight alterations in a shot shell crimp can have dramatic effects on the pressures generated in a given load, perhaps even more so than in a rifle load.

Yes sorry I should have said, shotgun.
I was specifically thinking caplock, however the principles are the same and interesting point re the vents/nipples, makes sense.
Older caplocks sometimes have "vents" on the side, I gather the theory of these being excess pressure relief.This would have an even more pronounced effect.
Forcing cones, crimp pressure, vents, nipples, all in all a few variables which could go either way.
Drew I will read through the link you have kindly provided.

I really wish I could remember where I read about the slotted chambers, perhaps it was GT Garwood.
Anyhow supposedly they were cut right through the length of the chamber and fired with normal loads to no ill effect.
If I find it Ill post.

Cheers,

GDU.

I've read before that those vents were not to vent excess pressure, rather a theory at the time that the then new percussion system suffered a disadvantage in that the powder couldn't "breathe" to achieve best combustion, like the old vented flint system.

Whether a like for like muzzle v breech/cartridge load would develop more or less pressure is an interesting question, regardless.

Cadet's reason for the "Vented" percussions is also the one I have always heard. Some folks thought they needed to get Air for better burning. Of course the powder had its own built in oxygen supply, it could not have received enough through that little vent without it.

To answer the original question we really have to keep all other parts of the equation on an even basis. In my opinion we need to stick with ML'ing caplocks versus breech loading blackpowder shells with equal loads of powder & shot. Using smokeless in the shells would add a far different variable.

Black has the unique feature of burning at essentially the same rate regardless of outside influences. It would thus be far less sensitive to minor differences in Crimp Strength etc as would smokeless.

The original question though only asked about the two systems. "IF" the question was which has the higher pressure a black powder ML'er or a Smokeless powder breech loader the Breech loader will win for certain.
Gotta compare apples to apples, not apples to oranges.

I wonder if any testing has actually been performed?

Theoretically, a cap lock with a mainspring strength igniting a properly sized cap on a cone with the proper sized hole bored through it should have minimal is any pressure lost back through the cap as the hammer fall after ignition holds the cap in place in effect sealing it. In reality as springs, hammers and cones wear and passages foul things do change. I spent years competing with ML rifle muskets and know full well the effects weak main springs, worn hammers and flame cut cones and filthy ignition channels have on accuracy.

Additionally I wonder about the pressure difference between a ML and a breech loaded crimped cartridge with equal powder loads, wadding and payloads. Theoretically the crimp will cause a minor and temporary increase in chamber pressure as the crimp unfolds but wonder if this is enough of a reality to make any difference in pressure, velocity or pattern.

Dave Myrick

I recall seeing some "Old Info" where they measured the pull necessary to open a crimp. There needed to be enough that the crimp would not open on firing the other barrel, but not so much as to raise pressure unduly. I have never seen a comparative measurement between crimp strength & a tight fitting overshot wad in a ML'er. The tight wad was necessary in the ML'er to prevent the charge from moving forward when firing the other barrel. I seriously doubt there is that much differences in the tight wad & opening a proper crimp in a paper shell though.

True, the difference may be slight, but there would be a difference. A more significant difference would be related to over bore sized wads pressing through a forcing cone. Something that is entirely unrelated when comparing to a muzzleloader.

Many early breech loading shotguns took thin walled brass hulls which were designed to be loaded with larger than bore sized wads in them. i.e. 11 gauge wads in a 12 gauge gun or 9 gauge wads in a 10 gauge gun. There would certainly be a difference in pressures, with everything else being equal, between a muzzleloader and breechloader with those loads.

Having said all that, I am not saying those difference are dangerous or even significant. Just pointing out there would certainly be differences between the two guns relating to pressure.

As of now I have not pitched my tent in either camp. There are factors in both systems which could cause changes in the pressure. Keep in mind what is normally measured is Max chamber pressure, while in reality we have a pressure curve extending the length of the barrels. Max pressure will normally occur just as the charge starts to move. There is no doubt the forcing cone can have an influence on the pressure curve, but it may not actually raise the max pressure as the charge is moving & pressure is falling prior to hitting the cone.

This is a pressure-time curve, possibly Hodgdon Clays from http://www.arizonaammunition.net/

Note the small primer spike then the powder combustion



Courtesy of Neil Winston and similar www.claytargettesting.com



Pressure - distance curve from "Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics" by Wallace H Coxe; E.I. du Pont de Nemours & Co., 1933 promoting DuPont MX (which sorta became PB)



Pressure - distance curve from the Alliant site



I don't see any evidence of a pressure rise, or interruption of the fall in pressure, when the ejecta "slams" into the forcing cone

Pictures are nice, but number would be better however

Drew;
I may not have worded my post well. I was not saying there would be a rise in pressure when the forcing cone was hit. As mentioned the pressure is falling upon hitting the cone. There "May" be a slight lag in the rate of fall. These results were so far as I am aware of were all taken with breech loaders so doubtful we have similar ML'er curves for comparison.

You don't?!?! Since the ejecta will be entering the forcing cone before it's entirety has completely exited the hull, it's impact on pressure would be measured in the first 1-2 inches of the barrel, right where the highest pressure spike occurs.

It's not as if it is exiting the hull in it's entirety and traveling unrestricted through open air, and then "slamming" into a forcing cone as you put it.

While this discourse is interesting. The only way to prove this one way or the other would be to come up with an actual pressure test. One would have to come up with, as much as possible, two identical loads for both a muzzleloader and a breechloader and pressure test the guns. While it would extremely interesting, it doesn't really serve any purpose other than satisfying curiosity. Alas, I don't foresee Sherman Bell doing one of his fantastic test runs on this topic.

If I were a betting man, I would put my money on pressures being higher in the breechloader. As to what degree however, I could not say.

Apparently I don't understand internal barrel ballistics

A pressure - time curve with those same loads



A distance of the ejecta - time curve



Peak pressure with e3 is about .0003 sec. at which point the ejecta has just started to move and has not yet "slammed" (did you miss the ?) into the forcing cone - at .0005 sec. - when the pressure is now falling??

I clearly need the help of a ballistic engineer to understand the contribution of the ejecta entering the forcing cone to peak pressure. I'll look around Neil's site
www.claytargettesting.com

toward the bottom here are some links about "chamberless shotguns"
http://www.trapshooters.com/threads/model-12-forcing-cone.286074/

I have been studying your charts, thank you for providing them. According to them at .0003 to .0005 seconds the ejecta, has not only started to move, it has traveled about an inch. At that point it has overcome the crimp, and has ENTERED THE FORCING CONE. There is no gap in time or space for that process to complete itself.

I have read through the links you have kindly provided, frankly they are not relevant. While they discuss patterning, felt recoil, barrel safety, etc. While interesting, they do not discuss pressure changes do to the modifications.

So to summarize your position if I might. Crimps and forcing cones have zero affect on the pressure of a fired load. And the peak pressure in a muzzleloader will be identical to that of the breechloader when they fire a similar load. Do I have that correct?

Thank you for looking into the other sites.
I blew up the distance - time curve (with of course loss of resolution). How much of the ejecta (length of shot and wad) has entered the cone at .0003? How long does it take for the "legs" of many wads to collapse? Why is the pressure falling at .0005 with ejecta still in the cone? What does overcoming inertia vs. friction vs. some degree of constriction on the ejecta upon entering the cone have to do with the pressure curve? How much constriction IS there from case mouth to cone with modern shotcup loads?



I said nothing about crimps, or wad seating pressure, or plastic vs. fibre wads, the wad design, or internal ballistics of the shotshell.

Neither one of us KNOW the effect of the ejecta entering the forcing cone, nor can we answer (with numbers) the OP's question. Do I have that correct?

I would say between 1/2" to 1"


Because it has traveled approximately about 2" at that point and is exiting the forcing cone. If you remember your fluid dymanics you would know that pressure drops when matter exist a nozzle. It also increases velocity, but good luck measuring that inside of a gun barrel. I wish we could.

I don't know. My position is that it does to some, as of this point, unknown degree. As far as I can tell, your position is that it has no effect on it.



All of those things are not exclusive of this topic, nor can they be excluded when discussing peak pressures or time curves. My contention is they all have a factor to play, which sets shotshells apart from the muzzleloader.



I'm not sure. You seem to be very disagreeable to the idea that it has any effect. I'm simply stating it must have some, which I don't think is a reach.

I know from reading your many posts over the years you seem to have made contacts with experts in this field over the years, and have access to testing equipment most of us do not. This might be an interesting experiment to take on if you are truly curious about it. However, I would agree the outcome of those tests would mostly be academic without much real world demand, i.e. pressure curves in muzzleloading vs breechloading shotguns . I think this one will most likely stay in the realm of theoretical debate, probably for good reason and not be worth the time or money.

Now coming up with experiments to test the effects of different forcing cone shapes/lengths in regards to breech pressures...that might be a different story

" The Modern Sportsman's Gun and Rifle" by Dr J H Walsh ("Stonehenge"). 1882.

Thanks greenerguy. Hadn't thought about "Stonehenge"

The Modern Sportsman's Gun and Rifle: Including Game and Wildfowl Guns, Sporting and Match Rifles, and Revolvers
John Henry Walsh ("Stonehenge"), Volume 1, 1882
http://books.google.com/books?id=OLwUAAAAYAAJ
Vol. 2
https://books.google.com/books?id=kLwUAAAAYAAJ&pg=PA1

Ah Stonehenge! Read About him for years but never read his book. Thanks for that link Drew, have downloaded it to my computer, just haven't had time to read much of it yet. Will do so soon.