Gents:
My double shooting is practical and I'm not much into the technical end. So, tell me this: why do black powder double rifle loads kick so much more than the same ballistics shot with smokeless powder? Of course, we can only be talking about cartridges originally loaded with black, not nitro cartridges loaded with black.

The difference in recoil is magnified in the larger calibers. While it is noticeable in the .450, .500, and .577 bpe rounds, and 12- and 10-bore, it is significant in the 8-bore and even more so in the 4-bore.

Some have said it is due to the burn rate of black. Others have said that a large percentage of the black powder exits the barrel and that gives the extra recoil (like adding bullet weight). I don't know if I buy the second as the weight of the powder volume that exits the bore is really not that much weight (as a percentage of the bullet's weight).

Recoil is stiff in my 8 and 4 bores. When I shoot the same velocity with black I get kicked into the next zip code (example 1400 fps with a 1900-grain conical in the 4-bore). The black powder charge is 390 grains of FFg and the smokeless charge is 100 grains of Blue Dot. The DB is stiff while the black load really hurts.

Why???

Cal

It is simple physics and I am sure you already know this. You have to add the weight (much of it at least) of the powder to the projectile weight, as it is not all burned at once, but becomes a forward moving projectile until it is consumed. The mere fact that you have two or three times the weight of BP than you do of smokeless adds to the mass that must be moved forward, hence that increases the rearward impulse. It does not have to exit the bore to create recoil.
You can't change Newton's third law.

Hello Cal,

Its a matter of the weight of the powder.

I don't know the weight of your 4 bore rifle, but at a rifle weight of 20 pounds;

- the smokeless load generates 158.35 ft/lbs of recoil

- the black powder load generates 337.01 ft/lbs of recoil

that's more than DOUBLE the recoil for the black powder.

also, recoil velocity is 46% higher with the black powder; 36.6 fps vs 25.1 fps, so it "feels" even worse.

You can use this formula to plug in the appropriate rifle weight and data to get the exact figures for your 4 bore rifle.

http://www.shooterscalculator....ecoil-calculator.php

Of course, if the rifle is lighter than 20 pounds, the recoil increases dramatically.

Here are the formulas for calculating recoil velocity and energy. As you can see the weight of the powder and the velocity of the powder charge gas is all part of the calculation and can have as much influence as the bullet weight and velocity for cartridges using big powder charges such as the big blackies. Unfortunately the squares (2) have not copied over well in the recoil energy formula but most will know the formula as E = 1/2MV squared so you can work it out.

FREE RECOIL VELOCITY & ENERGY

Wg = weight of the gun in pounds
W1 = weight of the bullet in pounds
W2 = weight of the powder charge in pounds
Vg = recoiling velocity of the gun in ft/sec
Vp = muzzle velocity of the bullet in ft/sec
Vc = effective velocity of the powder charge = 4700 ft/sec (Sebert)
G = acceleration due to gravity = 32.16 ft/sec/sec
Eg = recoiling energy of the gun = ½MassxVelocity2

Momentum Formula Wg Vg = W1 Vp + W2 Vc

Free Recoil Velocity Vg = W1 Vp + W2 Vc / Wg
Or = W1 Vp + 4700W2 / Wg

Free Recoil Energy Eg = Wg Vg 2 / 2G
Or = Wg Vg 2 / 64.32
Or = ( W1 Vp + 4700W2 )2 / 64.32Wg

Thanks, mates. It's always an education here on AR.
Cal

On second thought, answer me this:
My 4-bore with a round ball. Recoil is stout with Blue Dot and very heavy with FFg shooting the same weight projectile to the same velocity. If I add bullet weight to equal the added weight of the black powder (290 grains) the recoil is still far less than the FFg load. So, it must be more than just the weight of the powder. Is the very fast burn rate of the black add much to the equation? If so, is there a math formula (such as the recoil formulas above) to assist me in this?
Cal

Hello Cal,

If you give the gun weight - bullet weight - powder weight - velocity, of the different loads, I'll compare them for recoil.

rifle weighs 22 pounds, two bullets are 1400 grain ball, 1900 grain conical, and 2150 grain paradox. Powder charges are 100 and 120 grains of Blue Dot and 390 and 440 grains FFg, Velocity is
1750 fps 1400 grain ball with 120 grains of BD
1400 fps with 1900 grain conical and 100 grains BD
1175 with 2150 paradox bullet and 85 grains BD

1750 fps 1400 grain ball and 440 grains FFg
1400 fps 1900 grain conical and 390 grains FFg
1200 fps 2150 grain paradox and 390 grains FFg

From memory but close.
Cal

quote:

Originally posted by cal pappas:
On second thought, answer me this:
My 4-bore with a round ball. Recoil is stout with Blue Dot and very heavy with FFg shooting the same weight projectile to the same velocity. If I add bullet weight to equal the added weight of the black powder (290 grains) the recoil is still far less than the FFg load. So, it must be more than just the weight of the powder. Is the very fast burn rate of the black add much to the equation? If so, is there a math formula (such as the recoil formulas above) to assist me in this?
Cal

Cal all the answers are correct! Having said that there is one thing that has not been taken into account in any of the answers.

In simple terms, one key is the fact that the black powder is an explosive and the smokeless is not! The initial ignition with black powder is an explosion, and then the burn rate begins for the rest of the burn pushing the unburned powder, and bullet down the barrel. The black load being more in volume, as well as weight combined with the initial explosion is the reason for the added felt recoil.

Math simply doesn't explain everything, in this case, in laymen's terms.

...................................................................

Cal, certainly the additional powder weight affects the recoil, but the burn rate is the real killer. Remember all the discussion on using RL-15 for its slower burn rate in order to reduce felt recoil? As Mac stated, black powder is explosive and not "slow burning", meaning you "feel" the full recoil effect over a shorter period of time.

Todd, I just knew your Rocket Science degree would come in handy someday :-)

quote:

Originally posted by cal pappas:
rifle weighs 22 pounds, two bullets are 1400 grain ball, 1900 grain conical, and 2150 grain paradox. Powder charges are 100 and 120 grains of Blue Dot and 390 and 440 grains FFg, Velocity is
1750 fps 1400 grain ball with 120 grains of BD
1400 fps with 1900 grain conical and 100 grains BD
1175 with 2150 paradox bullet and 85 grains BD

1750 fps 1400 grain ball and 440 grains FFg
1400 fps 1900 grain conical and 390 grains FFg
1200 fps 2150 grain paradox and 390 grains FFg

From memory but close.
Cal

Hello Cal,

given a rifle weight of 22 pounds,

1750 fps with 1400 grain ball and 120 grains of BD = 134.11 ft/lbs recoil energy - 19.81 fps recoil velocity
1400 fps with 1900 grain conical and 100 grains BD = 143.95 ft/lbs recoil energy - 20.52 fps recoil velocity
1175 fps with 2150 paradox bullet and 85 grains BD = 125.56 ft/lbs recoil energy - 19.16 fps recoil velocity

1750 fps with 1400 grain ball and 440 grains of FFg = 311.71 ft/lbs recoil energy - 30.19 fps recoil velocity
1400 fps with 1900 grain conical and 390 grains FFg = 306.37 ft/lbs recoil energy - 29.94 fps recoil velocity
1200 fps with 2150 grain paradox and 390 grains FFg = 295.83 ft/lbs recoil energy - 29.42 fps recoil velocity

I'd be curious if your shooting experience (felt recoil on your shoulder) correlates to these results.

Given the data, the 2150g paradox bullet with blue dot should be the most fun to shoot, followed by the 1400g round ball, also with blue dot. The 1400g round ball with FFg is likely the least pleasant to shoot.

I'd sure love to have this problem.

quote:

Originally posted by Biebs:
Todd, I just knew your Rocket Science degree would come in handy someday :-)

It's rocket surgery dude! Rocket Surgery!

Actually, I think that Gerard of GS Custom Bullets has a very plausible explanation. "Take it away Gerard..."

perhaps the fact that it appears to be an explosion as opposed to a controlled burn rate...

quote:

Originally posted by buckstix:

quote:

Originally posted by cal pappas:
rifle weighs 22 pounds, two bullets are 1400 grain ball, 1900 grain conical, and 2150 grain paradox. Powder charges are 100 and 120 grains of Blue Dot and 390 and 440 grains FFg, Velocity is
1750 fps 1400 grain ball with 120 grains of BD
1400 fps with 1900 grain conical and 100 grains BD
1175 with 2150 paradox bullet and 85 grains BD

1750 fps 1400 grain ball and 440 grains FFg
1400 fps 1900 grain conical and 390 grains FFg
1200 fps 2150 grain paradox and 390 grains FFg

From memory but close.
Cal

Hello Cal,

given a rifle weight of 22 pounds,

1750 fps with 1400 grain ball and 120 grains of BD = 134.11 ft/lbs recoil energy - 19.81 fps recoil velocity
1400 fps with 1900 grain conical and 100 grains BD = 143.95 ft/lbs recoil energy - 20.52 fps recoil velocity
1175 fps with 2150 paradox bullet and 85 grains BD = 125.56 ft/lbs recoil energy - 19.16 fps recoil velocity

1750 fps with 1400 grain ball and 440 grains of FFg = 311.71 ft/lbs recoil energy - 30.19 fps recoil velocity
1400 fps with 1900 grain conical and 390 grains FFg = 306.37 ft/lbs recoil energy - 29.94 fps recoil velocity
1200 fps with 2150 grain paradox and 390 grains FFg = 295.83 ft/lbs recoil energy - 29.42 fps recoil velocity

I'd be curious if your shooting experience (felt recoil on your shoulder) correlates to these results.

Given the data, the 2150g paradox bullet with blue dot should be the most fun to shoot, followed by the 1400g round ball, also with blue dot. The 1400g round ball with FFg is likely the least pleasant to shoot.

My shoulder is not scientific, but it does reflect your calculations.
Thanks,
Cal

quote:

Originally posted by Bill/Oregon:
I'd sure love to have this problem.

Bill:
Our next double shoot is August 13. If you have the miles come on up and spend a day with a few dozen nice doubles, shoot all of mine (including the 4), and stay at my home to avoid summer hotel rates (Motel 6 at $200 per night!).

Cal

quote:

If I add bullet weight to equal the added weight of the black powder (290 grains) the recoil is still far less than the FFg load. So, it must be more than just the weight of the powder.

You are exactly right. The powder/gas is traveling at a much much higher velocity than the bullet, and therefore disproportionately contributes to recoil.

In my semi-educated opinion, here's my dissertation on what I think happens: The primer ignites the base of the powder column, it begins to burn/detonate from back to front (barring a primer tube, another topic entirely) and the powder+bullet mass begins to move down bore. At this point the unburnt powders is just payload equivalent to extra grains of lead. As the powder burns it is converted into high pressure gas which of course drives the bullet.

Until just before the bullet exits the bore, most of the recoil has been the result of the bullet weight. If this were a static situation, Boyle's Law would say that the velocity of the powder was about half that of the bullet (ie, if the barrel is pressurized equally in every part, the center of mass of the powder charge is now the midpoint of the barrel by volume, whereas the center of mass of the bullet has move the length of the barrel in the same time, thus the powder velocity is about 1/2 the bullet velocity.) But this is a dynamic event, and pressure, while decreasing as the bullet travels down the bore, is highest at any given instant closest behind the bullet (there are some really cool recoiless autocannon designs that take advantage of this fact that actually open the breach once the bullet is ~1/3 down the bore with little impact on velocity but a big reduction in recoil).

Once the bullet clears the muzzle all hell breaks loose and (in my opinion) this is where the difference between smokeless and black rears its head.

The highly pressurized gas escapes extremely quickly, between 4000-7000fps depending where you look, and screams past the bullet. Although the mass of the gas is low, it has a disproportionate effect on recoil due to its extreme speed.

Black is worse for two more reasons than just detonation velocity. One, there is a LOT more mass of it needed to get the same bullet velocity. Two, while most smokeless charges are consumed in the bore, LOTS of black powder exits the muzzle as 4-7000fps solid particles propelled by that high pressure blast and burns outside of the bore. I know it doesn't matter if it is a particle or gas, but assume the unburnt powder is that closest to the bullet base vs a perhaps more gradual exit of the same mass if it were burnt and spread thoughout the bore volume.

Put another way, that particle of unburnt that had traveled down the bore just like an extra grain of bullet is now almost instantaneously accelerated from 1500fps to 4-7000fps in a transition that makes the powder detonation look glacial.

quote:

To digress even more into the topic of primer/flash tubes, I've wondered if such a tube to carry the spark forward to ignite the charge starting just under the bullet base and burning back towards the breach would reduce recoil and improve performance? The powder would then burn from front to back with the as yet unburnt portion not being needlessly accelerated down the bore. It would also increase the time required for gas and unburnt particles to escape the bore as they'd have to travel its length and therefore spread that momentum over more millisecs. It works in artillery and tank rounds, along with some extreme wildcats, so why not bore rifles? How to test and measure this? Thought and opinions welcome.

Bob

Ejecta mass and velocity equal muzzle energy and recoil energy.

If the powder charge and bullet weights were the same for black or smokeless, recoil energy would identical- the difference would be only in terms of velocity of the recoil- felt recoil.

The rate of bullet/powder acceleration would affect how the gun moves in response. A faster acceleration would mean a faster recoil experience- yielding a harsher felt recoil. Now, in this case almost quadruple the powder mass AND accelerate the ejecta faster (if this is true?)- you feel more recoil faster....

Even though the gun shoots the bullet at nearly the same velocity, are the POIs different? If the black is in fact accelerating the load faster, I would expect a lower POI compared to a longer bore time from the progressive powder- unless that effect is diminished as the black , although starts more violently, remains constant and less of it is available over time - a negative curve of pressure, compared to the slower initial force and an accelerated burn as the load moves....

Regarding burnt powder- the mass is still in play, just as a gas not a solid. In black and smokeless, no air is required- all the volume is available in the charge chemically- all the powder mass is involved in recoil, maybe minus a tiny volume that is static in the bore once the bullet and moving gases exit and pressure drops to zero ( the volume of the bore has to be replaced with something- all the air in the bore was pushed out ahead of the charge.

Interesting photo Rob placed of me shooting his 4-bore single. The bullet has exited the muzzle and so has a lot of flame and (perhaps) unburnt solids from the powder. Rob can tell yo the load.

What is interesting to me is the recoil has not come into play at all. The barrels are still horizontal and my shoulder has not began to be pushed back from the recoil yet.

The entire sequence will show me being pushed back a step or two as it was a charge for a heavy double in a lighter single shot rifle. Yes, I wore a pussy pad and it was a hell of a kick. But the stuff is gone from the barrel before the recoil sets in.
Cal

Cal, that load was 383 grains (14 drams) of Goex FFg under either a 2000 or 2133 grain conical. I don't remember which. One online recoil calculator says that is good for +360ft-lbs of recoil energy at 37fps.

I can say it is a heck of a lot, but as an aside I don't put much stock in recoil calculations for several reasons. Two guns may make the exact same recoil energy, but if one has a higher muzzle velocity that energy will be delivered in a shorter period and the felt recoil will be worse even though the numbers are the same. Imagine a locomotive rolling into you at 1/4mph. Tremendous energy, but not "sharp."

The second reason is that guns do not recoil freely. I suppose if we hung a rifle on a wire, tripped the trigger, and let it freely swing back to only then hit our shoulder the gun would reach its calculated recoil velocity, and thus recoil energy. In reality, we do everything humanly possibly to prevent the gun from getting a running start at us, which along with the added mass of our torso, prevents the gun from ever getting anywhere close to that theoretical velocity, and since the energy varied with the square of the velocity, it is much much less than the calculated number.

Having just bashed those calculations, I think the numbers are still useful tools for telling you that Gun A has heavier recoil that Gun B, but the numbers are just a very rough guideline and shouldn't be taken literally. 300ft-lb will feel worse that say, 50, but not 6 times worse.


Here's the whole sequence of Cal shooting that load. I've shot exactly one of these and do not ever plan to repeat!













These two are me shooting 12 drams of Goex FFg under a 2133 grain concial. You can see how far my head and upper body moved between frames. This is the reason I use smokeless 98% of the time now!




Bob

you're comparing an explosion (BP) to a controlled high-speed burn...

Omin-Bob;

While I understand your expression of free recoil compared to a held gun, still, the laws of conservation of energy and equal/opposite reaction must hold.

So, if the mass and velocity of a bullet is ejected in a givn amount of KE, the holder of the gun must absorb the same KE, albeit from a larger projectile therefore at a lower velocity.( minus a bit perhaps from unidentified variables in gas operations or angular momentum). No?

I agree with IHS. Black powder is an explosive, so all the energy is released in a very short time frame vs. a controlled rate burn where the energy is still released very quickly, but over a longer period of time than an explosion.
Peter.

Black powder is classified as an explosive, but it is a low order one. In other words, it burns via deflagration just like smokeless (as opposed to detonation via a shock wavelike a high explosive). It does not detonate all at once; in fact much of it usually exits the bore unburnt compared to smokeless loads that are often consumed entirely in the bore.

HP, it is momentum that is conserved and must be absorbed by the shooter, not the KE. Holding the gun adds mass and therefore lowers recoil velocity, which (since KE varies with the square of velocity) drastically lowers the actual recoil KE.

Cheers,
Bob

I almost regret this thread as I don't know what the hell any of you are talking about. All I know is black kicks more than smokeless, for the same velocities, in the bore rifles I shoot. You can't ask a school teacher to understand you rocket scientists!
Cal

quote:

Originally posted by cal pappas:
I almost regret this thread as I don't know what the hell any of you are talking about. All I know is black kicks more than smokeless, for the same velocities, in the bore rifles I shoot. You can't ask a school teacher to understand you rocket scientists!
Cal

I'll paraphrase a French expresssion, "When a physicist answers, I don't understand my question."

My experiences are the exact opposite. Case in point, I have a 10.5 lb Shiloh-Sharps 45-110 I load with 100grains of 2FG or 105gr of 1F and a 520grain bullet. My 450 NE I load with 98-100 gr of H-4831 depending on bullet either 480 Hornady DGX, Woodleigh or 450 NFs and recoil is SUBSTANTIALLY more.

quote:

Originally posted by cal pappas:
I almost regret this thread as I don't know what the hell any of you are talking about. All I know is black kicks more than smokeless, for the same velocities, in the bore rifles I shoot. You can't ask a school teacher to understand you rocket scientists!
Cal

I suspect you are right, Cal. The extra weight in the ejecta is what makes black powder kick more than the restrained powder loads of NFB. I find some of that other stuff mentioned a bit apocryphal, esp. this assertion:
"- the smokeless load generates 158.35 ft/lbs of recoil
- the black powder load generates 337.01 ft/lbs of recoil"

Though there may be three or four times the weight of powder in the black powder load, it is a mere bagatelle compared with the bullet weight, which remains the same.

quote:

Originally posted by cal pappas:
Why???

Cal

As stated blackpowder is an explosive. Unlike a smokeless propellant blackpowder remain the same burnrate(speed of combustion) regardless of compression. That´s why blackpowder starts with full thrust. Smokeless powder builds up pressure and the burn-speed rises. The volume of the propellant will matter in weight of gasses also. The weight of the gasses must also escape forwards leaving thrust backwards. That adds also to an additional recoil as weight(volume) of blackpowder is more than smokeless in order to drive the projectile the same velocity.