Black Powder firearms and muzzle velocity measurement?

[Turnup]

I was hoping to put an upper bound on the energy of a projectile from a given weight of BP. The amount of energy in BP is not dependent upon its grain size.

The maths are correct, unfortunately the (in)efficiency of realising that energy makes the number useless.

The rate of deflagration is admittedly different for different granularities and is also dependent upon the peak pressures achieved - the chemical energy contained therein is a constant by weight.

[tacfoley]

I was hoping to put an upper bound on the energy of a projectile from a given weight of BP. The amount of energy in BP is not dependent upon its grain size.

The maths are correct, unfortunately the (in)efficiency of realising that energy makes the number useless.

The rate of deflagration is admittedly different for different granularities and is also dependent upon the peak pressures achieved - the chemical energy contained therein is a constant by weight.

If your posit is correct, why then do we get more velocity out of a given weight of Swiss powder than we do for the same granulation of non-Swiss powder? Can it be simply because the Swiss use willow charcoal and British makers don't?

There are way too many vagaries in BP shooting - the amount, or lack of, compression of the charge, the bore-wear, bullet windage, temperature, humidity and so on.

tac

[Turnup]

If your posit is correct, why then do we get more velocity out of a given weight of Swiss powder than we do for the same granulation of non-Swiss powder? Can it be simply because the Swiss use willow charcoal and British makers don't?

There are way too many vagaries in BP shooting - the amount, or lack of, compression of the charge, the bore-wear, bullet windage, temperature, humidity and so on.

tac

Are there any British BP manufacturers any more?

Yes lots of variables, and different powders and different granulations do perform differently.

ME variations are not about the amount of energy in the powder, it's about the rate that the energy is released.

Variations in the source of carbon and method of carbonisation (the folks over at rec.pyrotechnics certainly rate willow charcoal, and IIRC mountain ash charcoal is also considered good) will have only a tiny effect upon the amount of energy in the powder (it's just chemistry). I contend that differences in ME from identical amounts of different powder (or even the same powder at different granulations) are directly related to differences in the rate of deflagration, faster giving a more efficient conversion of chemical energy into kinetic energy. The (surprising to me) inefficiency of conversion from chemical to kinetic energy in a firearm means that only a small improvement in conversion efficiency can have a significant effect on the resultant ME. Another major factor in deflagration speed is how intimately the constituents are mixed. The finer the constituents are milled, the faster the powder. This of course takes time in manufacturing and therefore increases cost. It may also be that the "better" charcoals are structurally more sympathetic to fine grinding.

I postulate that higher speed of deflagration will improve conversion efficiency in the following ways:

1) less heat loss during the reaction
2) less powder burning outside the barrel
3) less time for gasses to escape via touch hole/nipple/cylinder gap.
4) acceleration effect of internal pressure

....but none of this helps the OP.

Back to the thread:

Looking at some posts on the MLAGB website forum, it seems that the MLAGB range at Wedgnock has similar ME and MV limits to your range, up to .75 cal. I say "seems" because this is from a hearsay post rather than definitive information. The Wedgnock range has hosted MLAIC international competitions in the past so they ought to know a bit about it.

Severnsider, I suggest that you think about contacting them http://www.mlagb.com/wedgnock.htm and/or getting in touch with a branch of the MLAGB close to you.

[tacfoley]

Just to reiterate my last meaningful post - 'it would seem that his problem lies not with physics, but with a bunch of grey cardigan clackies with attitude.'

tac

[severnsider]

Thanks for that info Mr Turnup - all very helpful as usual. I have just been PM'd by a Wedgnock member and may get in touch with them as you suggest.

[powderburner]

Just to answer the "is BP made in the UK"... the answer is no..

The last dedicated gunpowder mill closed in 1954 in Roslin, just south of Edinburgh. It was run by ICI who closed it as the buildings were being damaged by subsidence caused by local mining, and the licence was withdrawn.

The incorporating mills were moved to Ardeer, ICI Nobel's main plant where they ran up until the 80s but were not used for making Black Powder. The mills were only used to manufacture meal powder for making safety fuze. As I understand it no pressing or corning took place at Ardeer and corned powder was imported from Troisdorf, Germany for resale as Curtis's and Harvey's and for pyrotechnic use..

I would agree with your advice that it is impossible to predict GP performance from the chemical makeup. There is wide variation based on milling time, density, grain size and moisture content...