What influences black powder burning efficiency?

[Bad Ass Wallace]

Conducting some tests with burning efficiency of black powder cartridge guns. Normally I load the 38/55 with Swiss No2 (3F) which burns very cleanly as determined by wiping the barrel after every shot and noting the fowling on the patch.

Having been given a few part tins of various powder, I thought I would burn some up, first 'Elephant FG' 50gns in the 38/55 using my tried Paul Jones 375gn custom lathe bored bullet was tried and I found that it burned exceptionly clean with hardly any residue on the patch. Switching to the same load but with a 220gn Westcasting there was approx 3 times as much fouling and even some unburnt granules.

Thinking about it, the much larger bullet doesn't move as quickly as the smaller one, creating a much higher pressure peak in the cartridge case as the powder burns. Thinking back to the high school physics P1V1T1=P2V2T2, if the volume doesn't change (i.e. the heavy bullet doesn't move and therefore change the expedential volume in which it burns, the temperature must get hotter within the chamber, thereby burning the powder more efficently.

https://i.imgur.com/G1Y3yr2.jpg


Today I switched to the 50/70 firstly using a Lyman 425gn bullet followed by a CBE 520gn one. The same thing happened, the heavier pill load burnt cleaner than the light one (but not a dramatic difference as in the 38/55

So have the 'experts' got it wrong? It is normally recommended that the bigger the bore the courser grade of powder should be used.

The next set of tests is to try some loads of 3F and 4F in the same rifles, and in my muzzleloaders which range from 0.446" to 0.577". There are a lot of big heavy boolits for those also!

https://i.imgur.com/y7wVnki.jpg

[indian joe]

Conducting some tests with burning efficiency of black powder cartridge guns. Normally I load the 38/55 with Swiss No2 (3F) which burns very cleanly as determined by wiping the barrel after every shot and noting the fowling on the patch.

Having been given a few part tins of various powder, I thought I would burn some up, first 'Elephant FG' 50gns in the 38/55 using my tried Paul Jones 375gn custom lathe bored bullet was tried and I found that it burned exceptionly clean with hardly any residue on the patch. Switching to the same load but with a 220gn Westcasting there was approx 3 times as much fouling and even some unburnt granules.

Thinking about it, the much larger bullet doesn't move as quickly as the smaller one, creating a much higher pressure peak in the cartridge case as the powder burns. Thinking back to the high school physics P1V1T1=P2V2T2, if the volume doesn't change (i.e. the heavy bullet doesn't move and therefore change the expedential volume in which it burns, the temperature must get hotter within the chamber, thereby burning the powder more efficently.

https://i.imgur.com/G1Y3yr2.jpg


Today I switched to the 50/70 firstly using a Lyman 425gn bullet followed by a CBE 520gn one. The same thing happened, the heavier pill load burnt cleaner than the light one (but not a dramatic difference as in the 38/55

So have the 'experts' got it wrong? It is normally recommended that the bigger the bore the courser grade of powder should be used.

The next set of tests is to try some loads of 3F and 4F in the same rifles, and in my muzzleloaders which range from 0.446" to 0.577". There are a lot of big heavy boolits for those also!

https://i.imgur.com/y7wVnki.jpg

Wallace
I believe your theory to be correct - ie that heavier boolits make for cleaner burn of the same powder - we used a fair quantity of Chinese fireworks powder when things got tight supply wise earlier this century - you probably know the stuff - came outta Brisbane - the Belmont boy's were sourcing it - first lot we got seemed ok stuff (about 2005 or 2007 - second lot branded 2011 was hellish dirty) -what we got was 4FA - we screened it to FFFg,FFg,Fg - the FFFg in a 45 ML under patched ball was 'orrible fouling - FFg in my 45/70 under a 500grain pill was dirty still but not near so bad as the ML .....I sold the Fg to a bloke cheap for cannon use.
That powder shot ok - velocity was as good as Wano - just lots of fouling to deal with.
Lapping barrels makes a huge difference to fouling at my place - shooting a Uberti 45/75 and a Chiappa 1886 45/70 lately - the Uberti barrel just that bit more smooth and shiny and will shoot a longer string before it loses its edge from fouling - put an endoscope down em both and the Chiappa shows just a tiny bit of roughness in the bottom of the grooves - its an accurate barrel - better than I can hold with a tang sight.

[Wayne Smith]

The Army discovered this fact years ago. The 45-70 405 load did not burn all the powder, while the 45-70 520 load did. They ended up crimping the 405 load to delay it's movement and get full powder burn.

[Deadeye Bly]

As the pressure goes up the temperature goes up also. The higher temp and pressure gives cleaner burning of black powder. As noted heavier bullets burn cleaner than light bullets. It seems counter to logic but to get less fouling from black powder you need to burn more powder. Compressing powder in a cartridge generally will give less fouling as it burns hotter.

Shooting smoothbore muskets in the N-SSA is about the dirtiest shooting I've ever done with black powder. The ball has clearance in the bore and the pressures are low. Fouling builds up quickly and cleaning them after shooting uses up lots of patches.

[country gent]

I have found several things to have an effect on powder burn efficiency of the charge.
1) primers a primer can make a big difference in ignition and burn. Sometimes addition of a primer wad helps. My 45-90 load got into single digit ES with a aluminum foil disk. Fouling went down also
2) compression of the charge when the right amount of compression is found ES is lower and fouling is lessened
3) bullet weight heavier bullets allow for more complete ignition and a better burn. I dot shoot many "light" bullets in these rifles 38 cal-335 grns - 360rns, 40 cal 400 grns - 425grns, 45 cal 500grns-550grns.
4) crimp and or tension can also have an effect on powder burn and fouling. I normally shoot soft seated bullets with no crimp.

[GregLaROCHE]

Here are some pictures of charcoal greatly magnified. From an article I read (can’t find it again) the holes holes and crevices in the charcoal make all the difference the other ingredients get into them and that results in a more efficient burn.

The quality of the charcoal seems to be the only significant variable in BP. Better quality powders have selected the best wood transformed it into charcoal the best way possible to maximize the holes and crevices.

https://www.google.com/search?rlz=1C9BKJA_enFR735FR737&hl=en-US&ei=lC8cXa3VFpG8Utu3k-gO&q=scanning+electron+microscope+charcoal+black+powd er&oq=scanning+electron+microscope+charcole+black+pow der&gs_l=mobile-gws-wiz-serp.1.0.30i10.3002.25707..34309...0.0..0.987.1813 1.5-1j21......0....1.........0i71j0i67j0i203j0j0i22i30 j33i22i29i30j33i22i10i29i30j33i10i160j33i10i21.5p1 SgkkuSw8#imgrc=bezY4r_0VdReLM:

[Toymaker]

Some years ago there was a bit of research published in the MuzzleBlasts magazine. It showed that, in this instance, Goex FFg and FFFg burned most efficiently when compressed with 65 pounds per square inch.

I remember spending several hours over a couple of days practicing with the bathroom scale before I realized I had it all wrong.