Black powder felt recoil?

[Greg Mercurio]

For Hogpost:

The mass of ejecta, burned or unburned is equal. Mass of gas or mass of unburned BP is the same regardless of state. The only way to increase the mass of the ejecta is to add mass to the bullet or the powder. It can't magically happen at ignition.

I'm also challenging your statement that BP has a faster burn rate than SP. If it's true that BP ejecta is 50% unburned, by definition the burn rate is in fact slower than SP, as the burn "event" is of much shorter duration with SP. Not sure I could make the claim that 50% of the ejecta in an SP charged rifle is coming out of the barrel unburned. I suspect pressure/time curves would prove this out.

But that's just my opinion. YMMV.

[Greg Mercurio]

My suspicion on felt recoil is that the BP event duration creates the impression of a larger thump than with SP, even though the G-forces applied to your shoulder are roughly equvalent. The math doesen't change whether it's BP or SP. Mass is mass. Yes there is a velocity differential, and that is also perhaps even more causal than the mass component of the equation, but it's late, and I'm hugry, and not inclined to dig out the calculator to run "what-ifs".

You can test this endlessly here:
http://www.handloads.com/calc/recoil.asp

In terms of the dreaded physics, the human body percieves G-loading very differently than a lab instrument. You might not even feel a G-load of 15G's for 15 milliseconds, but spread that same 15 G's over 300 milliseconds, you will perceive all manner of different sensory inputs. The Air Force did a ton of Human Factors testing over the years after WWII to determine how the body responds to G's as the piston aircraft were replaced by the first generation of jet fighters. Most if not all of it is available if anyone wants to pore over old data.

Just one old coot's opinion, nothing more.

[LUBEDUDE]

I normally shoot smokeless in cowboy matches. But when I do shoot BP, wow, what a breeze. It feels less to me, more like a push than a snap.

Don't care what the facts are, recoil is all subjective.

[RMulhern]

Anyone that can't stand the felt recoil of a BPCR needs to stick to a .22 LR!!

[hepburn45110]

I have a Highwall in 40/65. I use a 370gr bullet and breech load 1/16 ahead of the case with black or smokless. The gun is loaded for 1260fps with both powders. A 50 shot match with smokless is not unpleasant. A fifty shot match with black is much more tiring. With black, the initial shock is a bit softer but it lasts longer. The rifle moves back further and twists a lot more making it more difficult to control with black. I think that the burn characteristics and powder colum weight of black cause this.

[bigted]

here is a fun thing to do when you try to pass off the "mass is mass" theory.......

load a 45-70 case with 50 grains of 3031 behind a Lyman 457125 520 grain boolit.

now load this same boolit with 50 grains of 2 f black powder and fill the rest of the case with cornmeal to the bottom of the boolit so it compresses the column around 1/8th inch.

now take your trusty Ruger # 1 out side and shoot the bp load first.......then touch off the 3031 load after and reply which one "felt" heavier.

mass is mass indeed...may make sense on paper but lacks something in reality.

[Hogpost]

Dang, Greg, you are absolutely right! I had forgotten my high-school physics: gas is mass. Apparently so have some prominent writers like Randfy Wakeman (ChuckHawks) who says "“Black powder and black powder substitutes are horrifically inefficient propellants; fully half of the powder charge does not change to gas, remaining a solid all the while. That gets pushed out your muzzle as well, and adds to recoil.”

So it's the full powder charge mass that is additional to the bullet weight, not just a part of it. (Although not all of it will exit the muzzle at the same velocity as the pressure drops quickly when the bullet exits, and some of the crud, as we all know, remains in the barrel as fouling.)

That's actually a better, more complete explanation of why a BP charge, ejecting the SAME bullet at the SAME velocity, provides measurably greater total recoil: it's the difference between 9 grns Unique and 38 grns FFFG in a 44-40.

(Again, this all refers to same bullet weight, same velocity: a SP load providing higher velocity, or using a heavier bullet, is apples-to-oranges.)

As to the burn rate of BP, what I meant by "unburned" refers to the chemical inefficiency of BP compared to smokeless: a higher percentage of the original charge remains as solid matter (fouling). I still believe that BP generally combusts more quickly than "progressive" SP, with the pressure generally peaking earlier; but I could easily be wrong, and there are undoubtedly exceptions in both direction. I'll try a couple of powder companies, and see what they say.

Thanks all of you for your inputs!

[Jeff Houck]

Here is the formula for recoil:
2
[(wght of bullet)x(mv)+(wght of powder charge)x(4700)] /64.348)x(wght of gun)

Weight of bullet is in pounds
Velocity of the bullet in fps
4700 is the velocity of the gas in fps
Weight of powder charge is in pounds

example 1 – smokeless powder (Unique)
500 gr. bullet = .0714285 lbs.
15 gr. powder = .0021428 lbs.
2
[(.0714285 lbs.) x (1150 fps) + (.0021428 lbs.) x (4700 fps)] / (64.3480) x (12 lbs.)

2
[82.14 + 10.07] /772.18

2
[92.21] /772.18

8503.41/772.18

11.01 lbs recoil

Example 2 – black powder
500 gr. bullet = .0714285 lbs.
70 gr. Powder = .010 lbs.
2
[(.0714285 lbs.) x (1150 fps) + (.010 lbs.) x (4700 fps)] /(64.3480) x (12 lbs.)

2
[82.14 + 47.0] /772.18

(16677.91)/772.18

21.60 lbs recoil


So there is almost twice as much recoil from the black powder load verses the smokeless loads of the examples. The difference is in the amount of recoil generated by the mass of the two powder charges:
15 grs. of smokeless = (.0021428 lbs.) x (4700 fps) = 10.07 lbs fps
70 grs. of black = (.010 lbs.) x (4700 fps) = 47.0 lbs fps

[Jeff Houck]

O k - so much for the posts maintaining the correct formating.
the "2" that appears on it's own line is actually the square that should be above the numerator line in the equation.
it should be: [(wght of bullet x velocity)+(wght of powder charge x 4700)] quantity squared. divided by the (wgt of the gun) x (64.348) = recoil

[Multigunner]

Well Black Powder is a Class A explosive, I figured its explosive rating compared to smokeless powder was due to its burning rate. A cardboard container of BP will explode when the same container of smokeless will only burn. Thus the more stringent requirements for storing BP even though less energetic per weight.

Older BP era shotgun barrels often have much thinner walls from a point past the chamber to a point before the muzzle. I think the term is "swamped". Gunmakers used this as a weight reducing measure for double guns. They could get away with it because the power curve of the BP charge peaked early. This is cited as a reason for otherwise strong BP era barrels splitting when smokeless powder loads were introduced.
It could be that the difference was only with early smokeless formulas that had many other incompatability problems.

Grain size and coatings determine burn rate of BP powders, smokeless burn rates are more due to formula and additives, though grain size remains a very important factor.
The surface coating of BP grains is a product of the solvent used in mixing. French powders were mixed using wine instead of water, natural polymers in the wine formed a moisture resistent coating on the surface of the granules as it dried. Don't know what modern manufacturers use to obtain this effect.

[Hogpost]

Perfect, Jeff, thank you!
I was curious about the selection of 4700 fps for gas velocity, so did some investigation:

"The NRA Fact Book (1988) gives some estimates for (gas velocity). For small arms, the gas velocity is about 4000 fps for smokeless and about 2000 for blackpowder. For cannons 4700 is used. Other references give only the 4700 fps figure."

"In the British Textbook of Small Arms (1929) it is suggested one make the propellant's velocity proportional to the bullet's: V = ( b + k*c ) * v / W

Unfortunately, the value of k was found to vary and "lies between 1 and 2, with an average value of 1½." If one uses that 150%, this equation at a muzzle velocity of 2700 fps gives the same results as the 4000 fps number cited in the NRA book. It seems reasonable to me the propellant's velocity will be related to the bullet's, but the fixed 4000 fps term gives a slightly better agreement with the recoil computations from the internal ballistics simulator QuickLOAD."

So, 4000 to 4700 seems about as close as one will get for smokeless, but the intimation is that it will be slower for black powder. Nevertheless, the difference will not be vast, and the formula points directly to the higher recoil from BP for th same bullet at the same velocity.

Cool!

[OD#3]

I got a "kick" out of the posts that suggested BP loads actually recoiled less and that the "felt" recoil was subjective opinion based on the timing of the total applied recoil load. I think that the ones posting these opinions must shoot only BP cartridge rifles. Were my only experience with BP cartridges limited to my .45 Colt-chambered model '92 replica, I might even agree. But with revolvers, my load of 40 grains FFF behind a 255 grain pill feels like a magnum load in my 7.5 inch barreled Colt SSA even though velocities rarely break 1,000 f.p.s. And even though I'm getting less than 650 f.p.s. from my load of 18 grns. FFF behind a 265 grain pill in my .455 Webley (actually .45 ACP, but I load it as if it were a .455 Mark I), the recoil is much stouter than I get with mild smokeless loads producing the same velocity. The recoil I get with black powder is so much higher than comparative smokeless loads, that I have even wondered if it was more punishing to the firearm than a smokeless load--despite the lower pressure. I've often wondered about the possible irony of my trying to "baby" my Webley Mark I revolver by using only low pressure black powder loads only to have it suffer damage of another kind by increased battering from recoil.

[ColColt]

I once had a Navy Arms Rolling Block half round/half octagon carbine in 45-70. I'd occasionally use about 65 gr of 3fg best I recall behind a 405 gr lead boolit and it seemed to "push" more than smokeless powder but not snappy like smokeless. I got the same feeling using BP with the 45 Colt but what a joy to shoot!

[juniorsonic]

I know this may sound like a cliche, but I have always found the 'recoil' from BPC guns (especially rifles) to be very much more of a big, somewhat slow "PUSH", rather than the sharp "kick" or "punch" of smokeless magnum-powered numbers. But that's just me.

[RMulhern]

Those that claim/bitch about recoil must be young and tender!!

[juniorsonic]

Those that claim/bitch about recoil must be young and tender!!

Yeah! "Recoil?" What's that? Well, to ME, "recoil" is merely the feeling of absolute proof that I am launching something capable of inflicting MANY ft-lbs of energy into/on anything in its path!

[Catlow Jack]

I know this discussion occurred over three years ago, but I'm new to the group and find this to be very interesting. This issue could probably be addressed objectively by running tests employing the use of transducers, specifically piezoelectric accelerometers, and a Tektonix 754C, 4-channel, digitizing oscilloscope (with color display). I believe I could set up and run the experiment, and provide some definitive answers in graphical form (force vs. time) if only someone would send me enough money to cover the cost of the equipment I'd need. $50,000 would probably be sufficient. Oh, and maybe you could also send a brand new Shiloh Sharps Rifle (Quigley Model) chambered for, say, .45-110, as a test rifle ... strictly in the name of science, mind you. I'd be happy to share the data ... and keep the rifle.

[Win94ae]

My black powder 50 cal rifle shots a saboted 250gr projectile about 1650fps. It feels a lot like the kick of my 44mag rifle propelling a 240gr projectile at 1700fps.

[M-Tecs]

I was always aware that the bullet weight and powder weight needed to be added together to calculate the total mass ejecta but I never fully understood how noticeably this effected felt recoil until I built three identical 6mm matches rifles. The chambering’s where 6mm BR, 6mm XC and 243 Winchester. The rifles weight was within 1 1/2 oz.’s of each other. When pushing 105/107's at the same velocity it was easy to feel the increase in powder weight in felt recoil.

[Hogpost]

Mr Catlow, sir: by any chance do you work for Da Gummint?