[P95Carry]

Guess this could be in ''reloading'' but it is more general than that really.

We have a thread going re burning up old nitro .. and this reminds me of an apparent paradox ... at least in part, as I view it.

Black powder in open air ignites with a rapid ''pooff'' - real fast..... nitro in open air burns with an energetic flame but slow ... more a sorta protracted and drawn out ''Shwwooooozzzzzzzzzzzzz'', albeit with considerable thermal energy release. (Excuse the phonetics!!).

Now compare in confinement ..... total opposite. Black powder tends to make a rather slow and ''relaxed'' .... ''Boooom'' .. and lots of smoke of course. It is used in places for blasting with slate quarrying, just because it is slow and being a deflagration as against explosive detonation .. much less brissant ... thus my choice of word ''relaxed''!! Does not break up the slate like blasting gelatin would .. which is best kept for rock with its brissance.

Now confine nitro and - RAPID combustion .... rapid pressure rise .. and very sharp and seemingly instantaneous result. Now under normal and safe conditions this is still deflagration - only in severe low case charge instances does it seem to detonate .. with nasty results!

It is striking tho to me this apparent dichotomy ... comparing confined and unconfined ..... mostly I guess pure academic interest. I know BP is just the humble 3 component mix and so one would think slower to burn .. but that open air ''poof'' is remarkable for its speed. There is too that rule with M/L's whereby no air space is meant to be left between ball and powder ..... what exactly happens when this IS done??

The nitro I have always assumed .. is ''self accelerating'' ... by which I mean that immediately after primary ignition, the pressure in case rises sharply along with temperature .. and this further reinforces the speed of burn ...... probably exponentially - but again ... how does BP seem so ''slow'' by comparison when confined.

Nitro IIRC is essentially a nitrated cellulose or glycerine .... depending whether double or single base .. compared with BP this is of course a non-polarized organic compound .. BP being exclusively inorganic and polarized. Both have available oxygen within their structure ... but .. how come these big differences beteen confined and unconfined?

I am not looking at the deep chemistry or physics here ... just mentioning something that intrigues me ....... if there are any actual explanations from those better qualified than I ... let's have em!!

Sorry .. my usual ramble!!:p

[pax]

Intriguing question.

pax

[cracked butt]

There is too that rule with M/L's whereby no air space is meant to be left between ball and powder ..... what exactly happens when this IS done??

If space is left betwen the ball and powder in a muzzleloader, the barrel could bulge behind the ball and cause what is called a 'walnut' or bulge near the breach end of the barrel.

[sm]

Black powder is a low explosive. BP can therefore 'blow" by sudden shock.
Smokeless powder is not an explosive , instead defined as a propellant. Designed to burn under controlled conditions.

This is how it was explained to me, This is why when the cowboys chunked a keg of BP over the wagon-side a new canyon was "blowed up" into being. :D

My Uncle said so when I was a kid, he let me shoot his guns,therefore he must have been right. :p

Chris...just what are you trying to destroy...this time?

[Azrael256]

If space is left betwen the ball and powder in a muzzleloader, the barrel could bulge behind the ball and cause what is called a 'walnut' or bulge near the breach end of the barrel. If you're lucky. If not, then the bbl splits. I've only seen it happen once, and the shooter only suffered minor nicks to his face (wear those shooting glasses!), but I wouldn't want to have a personal experience with it.

[P95Carry]

Chris...just what are you trying to destroy...this time? OMG !!! ...... http://www.bedford.net/design/images/smilies/lol.gif Hahahaha!

Hell man ... it's like you know me from all my life!! :D

Mind you .. in '85 I got my ''Shotfirer's Certification'' ... ya know ... blowing up rock faces - ANFO - Cordtex - 80% gel etc ... (licks lips!!) ....... perhaps cos I never really utilized it properly since ......... the ''blaster'' has yet to come out. :rolleyes:

Nah ... this time no great conflagratory plans ... it is genuine intrigue! Something I have never really satisfactorily answered.

The point re barrel bulge potential and BP ... OK that makes sense ... so that just leaves the main enigma.:p

[Mal H]

Chris - I believe your observation concerning BP may be flawed and that leads to the seeming contradiction. As I understand it, BP burns at the same rate in the open and under confinement and high pressure. If you took the same amount of BP and shaped it the same as it would be shaped in the barrel of a BP firearm and then lit it, it should burn at the same rate it would inside the gun. Of course it won't be exactly the same since it will most likely lose its shape which will affect the surface area and therefore the burn time (not rate).

OTOH, I believe your statement about any of the nitro compounds is spot on. The magical chemistry of nitro makes it burn at a much faster rate when under extreme pressure - almost asymptotically.

So, if I'm right about your not being right about BP, then there shouldn't be a dilemma.

Clear as mud?

[P95Carry]

Hey Mal!! "clear as mud" ... well maybe clear as primordial slime!! :D

No - you do have a good point and when viewed that way, maybe it helps a lot. Ok so ... BP then is we might say the ''constant'' .. same either way (tho still gotta say .. the BP ''burn'' under confinement still seems way ''relaxed'' .. ''leisurely'' .. know what I mean!?) My .577 Enfield, tho percussion ... seems to sorta 'pause' on ignition and then ''spit'' out the minnie! :p That of course could well still be the same speed of deflagration as unconfined.

So ... yeah .. perhaps the greatest change is indeed the confinement of the nitro and the ensuing ''runaway'' process..... giving that very rapid and sharp report ... not to mention that recoil can seem much more ''intense'' from nitro - a ''slam'' as against a ''shove'' .. compared with BP .. tho a full charge in a T Rex does seem ... shall we say .. ''authoritative''!!!!

[BamBam-31]

Whoa, I thought this was an American Gladiators thread. Sorry, I'm leaving....

:D

[Mike Irwin]

You're fairly close. Not bad for a Brit. :)

Black powder is, due to its speed of combustion, labeled a low explosive due to its burning rate. It maintains that burning rate no matter how much pressure it generates.

Smokeless powder, though, while generally have a lot more energy per unit, is considered to be a flammable solid, because it doesn't create the fireworks unless the pressure is contained. As the pressure rises, the faster it burns, which produces more pressure, which leads to even faster burning, etc.