Last edited by tacfoley; 05-11-2014 at 02:14 PM.
Thinking a little more about energy with BP, it occurred to me that a given weight of BP will release a reasonably predictable amount of energy when fired. I know that BPs are not all the same, but chemically they are very similar and the same chemistry and physics will apply. Could this help us to estimate how to stay within the OPs range limits?
So, I discover that 1 kg of BP contains about 3MJ of energy, which is 2.2M ft-lbs.
Quick calculation shows this to be just about 143 ft-lbs per grain.
Much more than I was expecting!
...and not at all helpful.
Clearly firearms are a very inefficient way of converting BP chemical energy into projectile kinetic energy.
Another approach is needed.
True freedom includes the freedom to make mistakes or do foolish things and bear the consequences.
TANSTAAFL
Providing that the shooters are not shooting a BP projectile faster than 1500 fps [the SAAMI .44 Magnum 240gr maximum velocity] there should be no problems. Since the British shooters tend not to have rifles of the Long Rifle type, and squirrel rifles that might exceed such velocities are rarer than rare things at a rare party, it would seem that his problem lies not with physics, but with a bunch of grey cardigan clackies with attitude.
tac
Last edited by tacfoley; 06-11-2014 at 07:17 PM.
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.
True freedom includes the freedom to make mistakes or do foolish things and bear the consequences.
TANSTAAFL
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.
True freedom includes the freedom to make mistakes or do foolish things and bear the consequences.
TANSTAAFL