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Discussion Starter #1
It just seems to me that a substance such as black powder, which detonates, should cause far higher pressures than a substance such as smokeless powder which burns at a predetermined rate. BP is classified as an explosive while smokeless is classified as a flammable... I don't get it. If I put 110 grains in a 54 cal rifle and seat a 230 grain ball on it and touch it off everythings great, but if I were to pour in 110 grains of Bullseye..... KABLOOIE! So why is BP (an explosive) so much less powerful than smokeless powder (a flammable)?
 

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JBar:
Here is a question I asked Hodgdon, and their answer. Might help answer your question.

Recently I picked up a 3rd edition of the Hodgdon Cowboy Action Data.
As I looked thru the loads, I noticed something that to me is a big question.
I have always heard, never use smokeless powder in black power cartridge guns. Use Black Powder or Pyrodex. Now I see the load data for the .45 Colt.
Using a 250 gr. bullet and 10.5 grs of HS-6 gives a load of 946 fps with a CUP of 13,300.
The Pyrodex load of 37 grs of "P" gives a velocity of 955 fps with a CUP of 13,500.
My question is, since the smokeless loads and the Pyrodex loads are so similar in pressure, how can the Pyrodex loads be less harmful on an old black powder gun than the smokeless loads giving 200 CUP less pressure?
I realize these are test barrel figures but so are factory loads. Please explain this to me.
Their Answer:
On the surface, your logic is accurate. BUT, what does not show on the
surface is how we get to these pressures.

If you look at a tracing of a smokeless powder pressure curve, it will have
a vertical or near vertical left side rising to a pointed peak which falls
away rather slowly on the back side. Kind of like an upside "V" with the
left side squeezed in.

If you look at a blackpowder or Pyrodex pressure curve, it is rounded in a
nice bell curve shape like an upside down "U"

While the two pressure curves get to the same height, they do it in a very
different manner. The time to peak is about 3 times longer for blackpowder
and Pyrodex than for smokeless.

All of this affects firearms in one basic way. The slower the pressure rise
and the longer the time to peak, the less stress on the steel of the
firearm. The steel has time to stretch and contract without tearing.

With fast peak pressures firearms must be designed to contain the stretch
before failure. Sometimes this is done with thicker walls on a barrel/chamber
and sometimes it is done by using different alloys of steel.

I hope that I have answered your question.

Mike





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Don't draw fire, it annoys people around you.
 

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Discussion Starter #4
OK, the detonation of BP is going to create a nearly instantaneous pressure spike, which will of course be the peak pressure, almost before the projectile even begins to move while smokeless is going to peak at a point somewhere midrange in the burn when the projectile is already well on it's way up the barrel..... so it still seems that smokeless should be acceptable as long as the pressure rating for the gun or cartridge isn't exceeded as it's going to be "gentler" on the gun, meaning it burns and builds to peak pressure instead of detonates and spikes instantaneously to peak pressure. I'm so confused!
 

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Jbar- there is a British tv documentary that I taped a while ago called "KABOOM"
In the show there is a lot of stuff about how gunpowder and explosives were invented and discovered, shows lots of fun stuff of things being blown up, even has a rocket powered bike demo that the boss of the British bomb disposal team recreated(seems he was a bit of a larrikin as a youngfella)
One of the mad/excentric Englishmen on the show explains the difference of the two types of powders.

When I did my explosives training I was told that B.P. is classed as explosive mainly as it is so easy to ignite accidentally, and therefore much more dangerous than modern smokeless powders, even though smokeless powder is much more potent than B.P. for a given weight.
If memory serves me correctly-and I might be wrong here- it also had to do with the burning rate of the 2 powders when unconfined as well, I think that B.P. still goes KABOOM in a big way whether it is confined or not, but smokeless just burns away happily when unconfined.
IF I AM WRONG PLEASE CORRECT ME!

Try and find a copy of the show as it is a real hoot to see what some of these fella's get up to.
If your video shop doesnt have a copy, maybe a t.v. stations archive will have it,
I have a copy but our video players work on a different system to the USA so it wont help much unless I can find someone over here that can convert it.




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stephen
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all times wasted wots not spent shootin'
 
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