A friend and I were playing around with some what-ifs yesterday, using a ballistics calculator to determine recoil. In addition to bullet weight, velocity and rifle weight, the program also called for charge weight.

Both of us are stumped as to why the charge weight of powder makes any difference in recoil, and I was hoping someone can give me the "Recoil Calculations for Dummies" answer to this question.

Recoil is a function of EVERYTHING that goes out the barrel, not just the bullet. It's true that the bullet is the biggest factor but the weight of the powder and the gasses and the muzzle pressure also contribute.

the powder, which turns into a gas and loses very little mass (this is not a E=mc^2 energy conversion), must also be expelled out the barrel. So its mass is part of the conservation of momentum equation. However, it is treated differently in the equations, from a standpoint of what velocity is it expelled at.

Part of the felt recoil is the impulse caused by the mass of the powder times the powder average escape velocity.
M(rifle)X velocity(rifle)= M[bullet]X Velocity[bullet]+M[powder]X avg. Velocity [powder gas]. Roughly, roger

Post deleted by ASS_CLOWN

A C,
It seems to me that you are leaving something out of your recoil equation. You have neglected to consider the fact that the body continues to feel pain long after the impulse which caused the tissue damage has passed.
I usually have to terminate an extended session at the bench with a 7mm or 30 cal mag due to lower back aches or shoulder bruises.
These stimuli persist long after the impulse of recoil has passed.
It may very well be true that my brain is not capable of registering the portion of the recoil caused by acceleration of the projectile. But it is capable of registering the pain caused by that impulse. I would assume this is true of most other people as well.
While this is an extreme example, let us consider the case of a rifle in 50 BMG.
A muzzle break can be designed to deflect enough gasses to the rear, so that the net effect of "rocket effect" is zero.
But if the rifle is chambered for such a large cartridge, the shooter must still be protected from the recoil impulse generated by overcoming bullet inertia. This is typically done by increasing the mass of the firearm.
A 700 gr bullet launched at 2900 fps from a 7 pound shoulder fired weapon would hurt, even if it were propelled by magnetic flux. And even if the pulse of said flux had a duration of less than 20 milliseconds.

My father used a book to design recoil mechanisms for the M107 and M109, "Elements of Ordinance" by Hayes." I think that is where he started using the formula that the powder [gas] escapes at 1.5 times the bullet velocity. I now see that ratio varying up to 1.8 on the internet.



I think felt recoil may boil down to peak pressure [psi] on the skin. That is how the recoil pad works, to spread the force over time and area gets the peak pressure on the skin down.



AC, those peak forces are what is available if there is no recoil movement of the gun.



Obviously even higher forces are possible if the recoiling gun is allowed to build up speed bounce off steel, but humans are softer and more compliant, and lesser peak forces would be recorded on at the skin.

Post deleted by ASS_CLOWN

I better log onto to this as I am a rockit signtist(sp?)sinetist anyways I are one for sure. The formula I use for recoil factor does use charge weight as one of the factors. The reason is real simple. A person that buys factory loads wouldn't know the charge weight,thus they couldn't use the formula. If they have been procrastinating(that's putting it off-- for you non scientist types)maybe not being able to use this formula will be the push to get them started--but that's another post. Anybody that buys factory ammo probably shoots a 300 mag anyways and all they need to know is that it kicks the fecal matter(thats scientific talk for crap)out of them. So for what it's worth,I'll list the formula. This does not give pounds--it only gives a recoil factor which can be used as a rule of thumb for comparison purposes. Despite it not registering how many milliseconds it takes your brain to feel it and how many milliseconds the force is applied--I find it to be a fairly useful guide. Take bullet weight(in grains)and add to powder charge (in grains)multiplied by muzzle velocity(in fps)and divide that by 3500. Divide that by rifle weight in pounds. This gives a recoil factor. Generally above 20 is a kicker. It is non linear.

There was a guy named Newton that came up with three laws. His third law states "for every action there is an equal and opposite reaction". In addition the Law of Conservation of Mass states that "matter can not be created or destroyed". So as I teach my High School physics students since the mass of the powder is converted into gases which exit the barrel with the bullet it is needed in the calculation.
See you only thought High School Physics was a waste of time.

""There was a guy named Newton that came up with three laws.""

Now really dndfloyd! Are you saying ass clown can't write a change notice to Newton's LAWS OF MOTION. Golly I think that's awfully one sided. roger

Just a little clarification here, AC, please...

Are you saying the nerve endings where the force is applied do not detect (experience) the recoil force for 40-to-70 milliseconds? Or, do you mean to say that the time required to transmit the felt pressure through the nervous pathways to the brain takes 40-70 milliseconds? There is a considerable difference in the implications of those two statements.

One says you never know what happens at the instant the blow lands, either consciously or subconsciously, while the other says that you feel what happens immediately, but don't realize it for some part of a second.

I suspect it is the latter you mean, or at least that it is the latter that is correct.

Alberta Canuck

I've spent just a bit of my life working in the field of psychophysiology and cognitive neuroscience... which kinda means I know a little bit about how the peripheral and central nervous systems respond to stimuli, and how that response is 'translated' by the brain to being what we call an 'experience'.



As far as I know, it ain't rocket science, and whilst complex, it isn't too complicated for a person who really knows what they are talking about to put a reasonably concise explanation on this forum...



Ass_clown... perhaps you might like to elaborate... I'd be interested to hear your stance...



If you're unable to provide a coherent and elegant precis, perhaps a few references that I (and others who DO know what we're talking about) could look up would be useful.



You also said:



"The human body isn't the quickest reacting system of sensors on the planet, although it is believed to be faster than the sensor array employed by the average lizard."



Oh yeah??? Believed to be faster by whom??



I look forward to your reply...

My understanding is that it's because the powder doesn't stay in the case, but moves forward as it burns... hence its mass has to be added to that of the bullet as it all moves down the barrel. What the algorithm is that takes into account the rate of mass reduction is, is beyond me... I could work it out, but have better things to do - that's why we have ballisticians. I would also hazard a guess that there might be some contribution from the 'rocket effect' of gasses exiting the muzzle - which would presumably also be a function of powder quantity...

I'm sure Ass-Clown could provide us with an elegent explanation...

belaw,
it's simple...

say you have a 30-06 with a 150 gr bullet.. and 50 grains of powder... the powder burns while going down the entire length of the barrel. it's assumed the powder burns at a constant rate, which is why it's not a perfect formula (i think it's about 7800 fps burn rate, but that's just a bad memory)

so, if you are launched 200 grs total weight, the recoil WILL change according to powderweight (and relative burning rate, but that's minor) as it's an equal and opposite reaction.

While when the powder exits the barrel, it's all burnt (perfect world) the gases and remaining powder still have WEIGHT (close to original weight, and close enough not to matter ) as the weight of the gases, + air burned - whatever is "lost" converting a solid to gas (aint much) will be the "weight" of the entire projectile.

think of it this way... if a pound of gas was introduced into a "perfect" vaccuum chamber that weighed 20 pounds, the weight would be 21#. it has inertia and mass, just not what you would conventionally think of as " a pound"

so, especially in bigger guns, a 500 jeffe-ry with a 535 grain bullet and 126gr of powder has a projectile weight of 651grs... obviously important.... even though that powder turns into a gas and leaves the barrel, it's WEIGHT (mass in one gravity)is still pushing back against the shooter.

jeffe

Lots of 'interesting' replys here, but I find it simplest to think about it as a solid fuel rocket engine. You are converting a solid to a high temperature, high pressure gas, then (when the bullet exits) funneling and ejecting it out the barrel of your gun. The more solid (powder charge) being burned, the more gas and the more thrust resulting, which is added to the bullet effect for total recoil thrust.

So for a brief instant, you are at the reaction end of a small rocket engine AND a slug thrower.

Or you can dissect the recoil formulas and trust that they are actually representative....your choice. Have fun!

Both of us are stumped as to why the charge weight of powder makes any difference in recoil, and I was hoping someone can give me the "Recoil Calculations for Dummies" answer to this question

belaw,

The basis of the recoil calculations is that the momentum of the gun will equal the momentum of what comes out of the barrel.

Lets use an 9 pound 300 magnum with 180 grain bullets at 3100 f/s and 80 grains of powder.

To get the momentum of the bullet

3100 X 180

For the powder we know the weight is 80 grains but its velocty is not so simple as some of the powder weight (now in gas form) will be at the very back of the case with no velocity. At the other extreme some of the gas might be leaving the muzzle at 7 or 8000 f/s. Recoil formulas assign an average velocity and the one that has been around for years is 4700 f/s

So for powder gas momentum we have

4700 X 80

Thus the total momentum of what comes out is

(3100 X 180) + (4700 X 80)

558000 + 376000 = 934000

The momentum of the gun will also be 934000. But that was all based on "grains" so we divide by 7000 to convert to pounds and then divide again 9 for the weight of rifle

934000/7000/9 = 14.82 and that is the velocity of the rifle in f/s

I would imagine that the 4700 f/s assigned to the average velocity of the powder gas was based on the 30/06. The 4700 might be a bit low for things like the 7mm Rem Ultra or 30/378 and probably too high for things like the 458. In other words the standard formula probably understates the recoil of 30/378 type calibres and probably overstates recoil for the 458 type calibres.

The recoil calculator on the opening page of www.huntamerica.com which I think was done by a poster on this forum called Customstox gives a bigger speed to the powder gas and as such it gives higher recoil for 7mm Ultra and 30/378 type calibres than does the old standard forumla.

Mike

For our ability to detect recoil, conservation of mass would be sufficient. THe weight of the powder is equal to the weight of the gas created during the burn. Granted, not all of the gas escaped and there is some residue that never exits the barrel, but throw all of that into the "ballpark" answer we are going to get anyway.

The powder burn is inefficient, no where close to approaching a pure mass-energy conversion where we would consider conservation of mass and energy (such as a nuclear reaction) The following link touches on this.

http://www.learner.org/channel/courses/essential/physicalsci/session3/closer1.html


For my purpose, I cant tell the difference in recoil while working up a load and increase powder charge by a couple of grains with a 150 gr bullet (and the associated increased velocity), so I take the equations with a sense of entertainment value only.

Post deleted by ASS_CLOWN

Merry Christmas to you also, AC and may all your groups be little ones. roger

AC, The reason I was asking for some references is because I HAVE been collecting and analysing data for some time, and I haven't seen anything that supports your premise in the way you have expressed... it might be that you have a little bit of knowledge of the situation, but just enough 'knowledge' to be dangerous... In other words, you haven't taken or investigated it further.



Now don't be gettin' your knickers all in a twist... there are some elements of your treatise that are 'sort of' close to the mark, (for example, the time it takes for a SINGLE impulse to travel along a SINGLE nerve) however, it's the interpretation of those elements, and how they interlink and inter-react with other serial, sequential and simultaneous brain processing functions that brings you undone.



You wrote:



"Most human brains seem to have a functioning sampling rate of 40 to 70 milliseconds..."



Individual neurons (nerve cells) may indeed have that 'sampling rate', however, sensory information is not conveyed to the brain by a single 'nerve'...as in a telephone line...



A very common mistake that many people make (especially engineers) is to fully adopt the brain = computer analogy. ie, totally linear in operation. It's a little more complex than that. It would appear that the brain works by a process sometimes termed 'spreading activation.' Let me give you a basic example... if I want to find a file on my computer, it has to undertake a sequential search of all the 'files' or data it has in it's memory. Which often takes quite a lot of time, and the process ends there. I can ask a person a similar question, and if they don't have that information (file), that person will know VERY quickly that they don't have the information. On the other hand, if they DO have the info, but can't immediately access it, you get the 'Tip of the Tongue' phenomenon... the person knows they have the info somewhere, but can't access it immediately... often the info will become available at a later time, when there are less salient factors to deal with. Yerkes-Dodsons model of optimal arousal sometimes comes into play here. Nerve impulses do not all travel down the same nerve, nor do they all stimulate the same 'processing area' in the brain. There are multiple paths, and many (if not most ) regions of the brain have 'projections' that stimulate other regions...



Bear in mind that there are something like 10 billion neurons in the brain, and each of those cells may have up to 20,000 connections with other neurons - some excitatory, some inhibitory, depending on what went before



Your 'sampling analogy' lets you down...



Anyway, enough with the technical stuff...



The situation that blows your argument out of the water is the matter of 'felt' or 'perceived' recoil.



Hunters often complain about recoil, yet 'feel' none when actually taking a shot at a game animal.



Others (like myself) are able to 'train' themselves to ignore the recoil.



The 'Laws of Physics' haven't changed, but how the brain 'interprets' those laws has...



Just to tie up the loose ends on the lizard thing, assuming the same body temperature, a lizard 'registers' a stimulus well before a human... the physical distance from 'sensor' to 'processor' is less.



Over to you...



And BTW your antagonistic, yet defensive attitude, combined with your fixation with being a 'moron' or 'imbecile' would suggest a state of mind that could use some help from someone qualified to deal with DSM-IV Axis II disorders before they become Axis IV disorders...



And you might recall that the original question was 'why is powder charge included in recoil calculation' i.e., easily answered using pure physics - YOU were the one who introduced this aspect of 'percived' recoil.



One last thought, the emotional state, physique and expectations of the person firing the firearm also come into play... now that's when it gets complex...

AZZ CLOWN Boy this is a subject that has been beat to death.Anyway There is one thing that all these calculations don't/can't take into consideration is the rate of recoil.Case in point ,two loads from my 30/06 in one load I use a pretty heavy dose of IMR4350 and the other H4831. Velocities are almost identical yet the 4350 load is pretty sharp whereas the 4831 load is more of a push which is more comfortable to my increasingly recoil sensistive shoulder.Sorta the differance between having a bowling ball thrown at ya versus one genty set in your lap.It's still a bowling ball!!! How's that for higher mathematics

284luvr, I've noticed the same thing in my 270 - faster burning powder seems to produce a 'snappier' recoil. Same bullet, same velocity.

I have never been able to buy the fast and slow recoil, I think it is in the mind.

When the bullet and powder gas moves up the barrel, say 22 inches, the gun will move back bullet

(bullet weight + powder weight)/gun weight X 22 inchs

you are talking about the gun moving back less than .1" and then the bullet clears the barrel. How far the gun moves back while the gases exaust, I don't know but it would hav eto be an incredibly small amount. Maybe all up the gun moves back .2" and then it is a projectile on its own.

I have seen plenty of people fire a few shots offhand from a 375 or 458 and say it is...a long push....but once it is their own rifle and they get it on the bench to test it they find it comes back real fast compared to their 7mm Rem or 270

If a 9 pound gun reachs 15 f/s in recoil I just can't see how it makes any difference to the shooter whether it got to 15 f/s via a 375 H&H or 300 Wby.

I certainly agree that a pereption is there but I think it is in the mind also the sound of the gun.

Mike

Mike, I can't explain it either - IMHO, the difference in burning rate would have negligible effect in the scheme of things, however, when I got my son to do a 'blind test' (ie, he didn't know whether he was getting a 130 in front of 2209 or 2213, and I wasn't letting him know) he stated that some of the rounds recoiled more than the others - and they were the ones with 2209...??

He tolerates recoil much better than I do, but was quite adamant... it's got me buggered!!!

As to the 'sound of the gun' - I couldn't agree with you more!!!

Go to St Mary's and see what happens when you're just about to take a shot, and the guy next door lets loose with a 458!! Instant flinch, no recoil, but I bet you'll pull your shot

Peter,

I have found much the same as you with the 270.

For the last 10 years or so I have used a bag of lead shot behind the butt. With the lead bag a 375 moves it back further than a 300 Win.

I think much of the basis behind people saying the small bore magnum kicks harder and faster is because it recoils more than it looks with the little bullet.

But the cold hard facts are that it is 458 type rifles that bust scopes and stocks and make scopes slip in the rings. As you know that is all to with the rate of acceleration given to the gun.

One area where powder could influence things is the velocity of the gas out of the muzzle and also the amount of unburnt hydrogen that ignites in contact with the air.

I have sometimes noticed that as loads have gone to real top end pressure that recoil has dropped off a little bit.

Mike

Yipes! All this makes it sound way more complicated than it really. (Well actually it is complicated when you try to put numbers on it). But back to the rocket analogy(which is a good one) and Mr Newton.

The backward thrust is going to proportionate to the mass of EVERYTHING that is expelled from the muzzle. If you load a blank (no bullet) there will still be recoil (a tiny rocket motor, if you will).

So, in the most elementary terms: More powder = more gas= more recoil AND/OR heavier bullet = more recoil. In short increase the mass of WHATEVER exits the muzzle, and recoil increases. (Yes, this is a most simplistic explanation, Calculating it is a whole different story.)

As far as first hand experience with "felt" recoil... My buddy and I worked up some 8x57 Mauser loads. I have a heavy gun with a recoil pad. We had a set of loads starting at a load of 2.5 grains less than max, as listed in the reloading manual, increasing in .5 grain increments to max. And I could "feel" the difference in recoil between the lightest and heaviest loads. Not a big difference, but noticable to me.

Also, as near as I can see, recoil MUST start the instant the bullet begins to move, again according to Mr. Newton. The entire process from ignition to the bullet leaving the muzzle is so quick you can't detect it except as one event, however. Right?

jeffe,

Powder weight will of course make a difference to the speed the rifle achieves.

I am also assuming equal weight guns.

If two different calibres have the same combined momentum of gas and bullet and one rifle ways 15 pounds and the other weighs 10 pounds then if the 10 pound rifle reaches 20 f/s in recoil then the 15 pound rifle will reach 13.33 f/s

Now let's say we reduce the power of the calibre used in the 10 pound gun so that recoil velocity only reachs 17 f/s it recoil energy will bed greater than the 15 pound gun

17 X 17 X 10 = 2890 Vs 13.33 X 13.33 X 15 = 2665

But momentum of the two guns will be

17 X 10 = 170 Vs 13.33 X 15 = 200

So the big gun will drive you back further.

But stick a 577 Nitro in a 8 pound gun and it will make a 7mm Ultra recoil seem like slow motion

Mike

Mike, I notice it more with pistols, but I feel the same effect applies...

Think about the difference between slow and fast powders during their burn. The fast powder hits peak pressure faster and declines faster, so the bullet+powder/firearm is accelerated more during the early stage of the firing process. Same (approximate) net thrust after the bullet leaves the bore, but more thrust in a shorter time for the first part of the process==snappier perceved recoil.

Thats my (admittedly less than completely scientific!) story and I'm sticking to it!

Post deleted by ASS_CLOWN

"My comments about sampling rate are straight from objective data acquisition, which typically involves a computer. "

Your Honour, the Prosecution rests its Case....

How do you explain that a 110g bullet out of a 270 definitely has less 'felt' or 'perceived' recoil than a 130g bullet when they both have the same muzzle velocity... 'double blind' experiment by the way...

As a research psych, these things intrigue me...

Recoil energy is kinetic energy developed when the round is fired. The momentum equation allows us to calculate the velocity of the rifle during recoil using the weight of the bullet, powder charge, and rifle. The bullet and powder exit the muzzle and impart energy to the gun (Newtons first law). Once the velocity of the rifle is known its kinetic energy is calculated using the mass of the rifle times the velocity squared. This is a scientific fact. It can also be measured in a laboroatory environment (there will be a minor loss of energy because of the elastic deformation of the rifle barrel, heat loss, and the manner that the energy is absorbed by the rifle etc..). I have read some articles where recoil was calculated and measured in a lab. The numbers are very close. The equations work. The only problem is measuring the velocity of the escaping gas. You cant do that outside a lab. Consequently most equations use an approximation that is a good estimate for 80% of the cartridges out there.

Felt recoil is impossible to calculate. There are too many variables including recoil velocity, differences in the shooter and the rifle, shooting position etc... It's no different than trying to compare the killing ability of a .223 to a much larger but slower round. Energy is the ability to do work. Even if two objects have the same amount of energy the way the energy is applied and the efficiancy of the energy transfer make all the difference. The kinetic energy may be the same, but the effect can be totally different.

And the winner is elkhunter by a nose. roger