# Low pressure smokless loads?



## Goshawk (Mar 3, 2009)

And in yet another area that I'm lost in:
Why can't you shoot smokeless in a good strong muzzleloader? Shotgun powders push 1+ ounces of lead out the barrel, never developing too much pressure, and from the loading data I've seen, are sometimes in line with muzzleloader pressures. So, assuming light charges that do not go past a specific psi, why not smokeless?
I know some of you who have been at smoke poles for a few years are mumbling "not again" but I'm new at this game and am trying to understand the inn's and out's as it were.
Thank,
Goshawk


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## honkerslayr (Dec 14, 2006)

From what I've always seen is that they can't handle that kind of pressure and are made specifically for black powder,not smokeless, dont quote me but I'm just saying thats what I've always heard. It's just a big no no.


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## barebackjack (Sep 5, 2006)

The problem with the added pressures of smokeless powders isnt necessarily with the barrel.

What does every muzzleloader have that centerfire weapons do not? A flash hole.

Every time you pull the trigger on a MLer, you have hot gases escaping from both the muzzle, and the flash hole, wether it be a nipple or flintlock flash hole. To much pressure through this small diameter hole, could prove to be disasterous. Even with BP loads through a flintlock, the hot gases can be severe enough to extremely burn somebody standing off to the lock side of the weapon (why military flintlocks were often fitted with flash shields on the lock to protect the next guy down the line).

Smokeless powders burn at much faster rates than BP or the subs. Try it sometime, make two lines of equal length of both powders, and touch them off, see what one is done burning first.
This faster burn rate creates much higher pressures very quickly, before some of that pressure is released by the projectile exiting the muzzle.

An easy way to think of the two powders is to think of BP as a burning piece of paper, and smokeless as a piece of paper soaked in gasoline. Much exaggerated, but you get the point.


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## rogerw (Jan 7, 2008)

Goshawk said:


> And in yet another area that I'm lost in:
> Why can't you shoot smokeless in a good strong muzzleloader?


The short answer is that "you'll put your eyes out!" or worse.

Modern Smokeless has roughly 3 times the energy density of blackpowder. Phsically this is because when BP fires, you get about 43% gas and 56% solids. The solids that suspend in the air are called smoke. The solids that stay in your barrel are called fouling. If more of this solid were to turn to gas in the combustion process, then more energy would have been released; the reason modern smokeless is smokeless is just that, about 98% of it turns to gas; ergo more energy from less powder, and no smoke or fouling by comparison.

If you make what is called a closed-bomb (entirely enclosed, does not explode, nor leak) and load it with a 100% loading of Blackpowder, when the powder is fired you will get about 96,000psi peak pressure (lessening as the gases cool from 2350dgC heat of combustion). The reason you NEVER see anywhere near this kind of pressure in your muzzleloader is that the bullet is always moving before the powder is fully burned, or even half burned. In fact, the bullet will have moved about 4-5inches by the time a heavy load is even all inflammed, much less burned up. Because the bullet moves forward, the gasses have an increased volume, lowering pressures from the closed bomb to only about 6,000 to 16,000psi depending on load.

However, smokeless puts 3 times the energy density in the same volume. Or, you say just load 1/3 as much? Just because you load 1/3 as much does not change the ratio of energy to volume of the load. In a closed bomb experiment you could expect about 3 times the peak pressure (energy = pressure x volume) and in the breech of a gun you could expect about 3 times the pressure as well. It really matters what VOLUME the powder has in which to initially burn! If you increase the energy density, you LOWER THE VOLUME (for a given energy) and RAISE THE PRESSURE, proportionately (keeping bullet weight constant).

AGain, in the smokeless breech, the bullet moves and increases the volume as the powder burns and you never see pressures like 300,000psi of a closed bomb, but you do see pressures like 50,000psi to 60,000psi (again, about 3x).

It is just as important the volume of the powder load, as its energy density in dtermining what the pressure profile will be. However, aggravating the smokeless is the fact that it burns faster under pressure and produces a sharper pressure rise and peak (called "Brisance"), which contributes to the pressure peak since the bullet does not move out of the way as fast to a sharp "rap," than a long slow pressure "push."

So, these are the reasons that a smokeless breech experiences much higher peak pressures. The nature of higher pressures does not simply go away because you use a lighter load, because the DENSITY (ENergy in a given Volume) has not changed. However, if you lower the burn rate of the powder, you have some control and this is what is done with Shotgun powders. MOre on this in a minute.....

If you look at a modern high power rifle breech you will see large lugs on the bolt which closes with the breech chamber. These lugs have a lot of area with which to receive the force caused by breech pressure and lots of beefy steel behind the area of contact. If on the other hand, you look at the way the breech is closed on a typical muzzleloader what do you have? You have screwthreads......how much area do you think this adds up to, and how much beeffy steel do you see on each thread behind that skimpy area? Do you imagine that those screwthreads can handle as much force/pressure as the lugs of the bolt of a highpower rifle? NO WAY! Ditto for anything else threaded in besides the breech, like a nipple, clean out screw, etc. In addition, because of the lack of need for it, the metal of a modern muzzleloader is often not the same grade as that of a high power rifle. The cap ignition with a nipple is an additional issue if the gun is not 209 primed, as BBJ poiinted out, though many modern Inlines dispense with this limitation and can therefore handle somwhat higher pressures.

Back to the Shotgun.....It took me a long time to come around to an answer because this is an interesting challenge to the whole premise.....A shotgun has a cavernous barrel, and therefore lots of volume is made available by relatively small movements of the shot-column, but muzzleloaders generally have somewhat large calibers too. In addition, Shotgun loads use a very slow burning (by comparison) smokeless, so that helps. But I think a key will turn out to be the wadding column......The wadding keeps there from being a space (before firing, volume between load and projectile is bad bad bad) and yet it collapses pretty well under pressure to create additional volume. I think that may be the key....but, I will readily admit to not being totally sure.

I do not personally understand why folks want to go back to a primitive configuration (ie, loading thru the barrel with loose reloading components) and then turn it into a modern experience by turning everything about the gun into a modern cartridge gun, except for the cartridge itself and retaining only muzzleloading instead of suppository loading. (actually, we all know why, it is an artifact of the way the State game laws were written back when muzzleloader = primitive.) But, as Galileo said, "and yet it is there!"

IMHO, stay away from smokeless unless the manufacturer expressly says it is ok. Even then, these guns have been blown up (at least one Savage with smokeless load) so be careful! And stay within accepted practices when you are putting thousands upon thousands of PSI pressure right in front of your face!

Realize that some of the substituteskys ARE smokeless duplex loads. IMHO the reason that they charge so much for these powders is that when you finally blow yourself up, they are going to get a large lawsuit, and the premium price is actually a premium on the insurance against that eventuality.

Be Safe, and don't try to duplicate your cartridge gun performance with a muzzleloader.

YHS,
rogerw


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## rogerw (Jan 7, 2008)

Here is a over-simplified illustration of what I was saying above, that the Volume of the Charge matters to pressure, in case it is not clear.

Imagine a .50cal gun with a 28" barrel, and imagine that the pressure in the barrel just before the bullet exits the muzzle is 1000psi.

Oversimplifying and assuming pressure is inversely proportiona to volume (that is, ignoring temperature change effects that are real when gasses expand), imagine that the bullet was originally seated 2" from the breech-face (and the powder had occupied this space). The pressure would have initially (and simplistically) been 28"/2" x 1000psi = 14,000psi.

Now imagine that the bullet was seated 1" from the breechface and the powder had twice the energy density of before.....the initial pressure would have been 28"/1" x 1000psi = 28,000psi.

Now imagine that the bullet was seated 1/2" from the breechface and the powder had 4x the initial energy density.....now the initial breech pressure would be 28"/.5" x1000psi = 56,000psi.

The muzzle energies of each of these shots would be comparable, except that the deeper seated bullets have slightly further to accelerate, and therefore measurably higher muzzle velocites, but only a few percent higher.

But the breech pressures would be totally different, even though in each case it drops to 1000psi as the bullet reaches the muzzle.

(now, you should keep in mind that this simplistic calculation is NOT accurate at all of how the pressure actually drops as the bullet moves up the barrel, because heat is lost to gas expansion (cooling) and to the barrel, etc and I have ignored those effects for the purpose of a simple illlustration. Because heat is lost which causes additional pressure drop, the correctly calculated breech pressures would have to be HIGHER than stated, but that does not change the point of this simple illustration.)

Your muzzleloader can handle 14,000psi but it cannot safely handle something North of 25,000psi.

YHS,
rogerw


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## darkgael (Feb 10, 2006)

Rogerw: Nicely done.

Pete


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## Goshawk (Mar 3, 2009)

Thanks for the detailed answer.
Well done.
Goshawk


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