Okay to start with, I am not a physicamatician. My credentials include having to take the same math class three times in college to get a passing grade (and only because I found a professor who gave multiple choice examines with a 15 point spread per grade letter instead of the standard 10. Ahhh, night school. ). I read the posts on the thread by Mr. Gould on the unique doubles, and also the thread started by AC, and didn't understand most of the dialogue on recoil.

Bottom line, is there a formula to calculate the relative recoil of cartridges for comparison without using the rifle's weight?

I look at cartridges is different classes. 30-06 and under kicks, but isn't so bad. The 338 and 375 magnums definately move you more, but no big deal. 40 cals start getting your attention.

When you move to 45 cal and above, and we're talking sporting weight rifles, no brakes, no lead sleads, then there is an extra bit of mental effort required to set off full patch loads w/o flinching, in short, they move you.

The calcs never did a thing for me, as what really matters is how it feels to you, and what you have to do to shoot it comfortably. Stock shape and weight definately help, but the adding or subtracting a pound doesn't make a huge difference, you still get rocked. It's when you make the rifle 25-50% heavier or lighter then std weight that you'll notice a difference, IMHO.

Ola Gringo!

First you have to decide "What is recoil?" MOst formulas give it in terms of kinetic energy, I suppose because we do the same with bullets. That has never seemed a very compelling case to me. Nor have I been too convinced that the figures I have seen bore much correlation to the wallop I received in the shoulder.

You could go with a momentum calculation (does this start to sound like a familiar debate?), but again I don't know how meaningful that would be. The truth is that recoil is a complex dynamic response involving time and mechanical behaviors related to barrel length and propellant burn rate, muzzle geometry and gun mass and recoil pad elasticity, etc. Recoil is not a scientific term as such. It could be taken to mean the movement of the gun or the force required to move it or the velocity of its movement or even the energy. Take your pick.

I am convinced that for some cartridges a very significant part of the recoil is a rocket effect of the gasses escaping from the muzzle. Otherwise a muzzle brake would do no good. Muzzle pressure is a term of some importance then, but having the same velocity and lower muzzle pressure would imply a faster powder that built up a sharper pressure rise rather than a more drawn out push. On the other hand, how much of that sub-millisecond business can you really feel? I dunno.

I talked with a guy who thinks that a 500 Jeffery doesn't kick as bad as a 416 Rigby or a 458 Lott. I am skeptical, even with the lower pressure, given the huge volume of powder being burned.

As for taking the gun weight out of the question, you can do a couple of things. Either make all the guns weigh the same and so normalize the results or else just ignore that term and make a number and call it relative recoil. For my money the quick and dirty approximation that comes closest is more like momentum than energy. Lacking any information on the force-time realtionship created by the internal ballistics, I would simply multiply the bullet weight by the muzzle velocity and add to this the powder charge weight multiplied by 4700 fps (ballpark figure for adiabatic expansion velocity on muzzle exit). Divide the whole shebang by any suitably large number to make it convenient. In the past I used 2700 fps for blackpowder loads. I don't remember where I picked up this value, so I can't judge the real meaningfulness of either quantity. Both are likely gross averages (or wild guesses).

There would be no "formula" to calculate that other than experience! I use the formula sometimes to get a general idea, but I have shot rifles that were much higher in "number" than another but felt like they kicked way less. Take for example- my 450 Dakota (loaded to the same as 460 Wby.) is far more comfortable to shoot for me than my 330. Although, that's not totally fair because the 450 does have a break. Without earplugs, it would be the other way though. The muzzle blast is hellish.

Rifle weight, stock shape and the presence and effectiveness of a recoil pad all have an effect. Also, the shooter and what he does or doesn't do with the rifle when and as he fires it have an effect.

There is no way to take these elements out of the recoil equation and have it make any sense.

But the formulas only include weight and essentially assume that all else (including the shooter's form) will be equal. They are good as general references and for making general comparisons, but only of the grossest kind. They will not tell you if "Rifle A" will "kick" more than "Rifle B."

The truth is that if "Rifle A" is a heavy rifle with a bad stock and no recoil pad, it will "kick" you harder than a substantially lighter "Rifle B" where the latter is equipped with a good stock (e.g., straight buttstock, rounded comb and wide butt profile) and an effective recoil pad.

So, to really know, you have to pick them up and actually shoot them.

I forgot one other factor that the calculations won't factor, the recoil pulse. I've only had it happen in one gun, and it is my 350 Rigby. I had developed two loads that drove a 250 gr to 2700 fps one burning 66 gr of Varget, the other 72 gr of H-4350. One would expect nearly identicle recoil, but not so.

The Varget load was what I expected from a medium bore rifle, boom, shove on the shoulder, no big deal. The 4350 load resulted in a nasty slap to my face from the stock with every round fired, and my comfortable medium bore was slapping me silly with each shot. Fortunately the Varget loads grouped much better then 4350.

I thing gun cranks way overdo calculations, whether for recoil, secitonal densities, retained energies, and other bs.

What really matters is what can be done to make it possible to shoot a big gun.

mrlexma,

Actually almost everything you spoke of can be mathematically modeled, and accurately too with proper correlation.

Recoil isn't that difficult to understand, if you have received the proper education.

These are the recoil force curves for several cartridges. With these one can ACCURATELY calculate the recoil momentum, recoil velocity, and recoil energy.



ASS_CLOWN

GP,
go to www.realguns.com and signup.. it's free, and you can use their recoil calc...


there's some people that will try to tell you things about recoil that make about as much sense as if they were trying to sell you a car, and when you ask about gas mileage, they try to give it to you in nanometers per calorie (and not even the kilo calorie that is used when you talk about food)

sure, if you take and do the math to to the particular situation.. but what's the point?

jeffe

jeffeosso,

If you knew anything about physics you would immediately understand that the so-called "recoil calculator" you are so hyped about is completely wrong in it's application.

I will give you a tiny hint. Newtonian physics is CALCULUS based! So the simplistic illustrative examples (high school and freshman level College physics so many of you are "proficient" at) you like to post are typically GROSSLY wrong (recoil being perhaps the MOST wrong of ALL of these examples of yours). Newton's greatest contribution to mankind was CALCULUS, not his first second or third laws. Heck the earliest cavemen understood the concepts behind Sir Isaac's first, second, and third laws. What no one had until Sir Isaac was the ability to prepare accurate mathematical models describing the events occuring due to Newton's first, second, and third laws.

Furthermore, the bullet DOES NOT conserve any momentum with the rifle, simply doesn't happen. Common sense alone tells you this, when does the bullet IMPACT the gun to transfer momentum? It doesn't! The gas expansion is a closed (read self contained) event and the shooter feels NONE of it. What the shooter feels is the momentum of the expelled gases (which are at high pressure and high velocity) striking the atmospheric air's mass. There is you momentum conservation, THE EXPELLANT GAS (BURNED GUN POWDER) IMPACTING THE ATMOSPHERE! By the way, that is PRECISELY how a rocket engine works, and that is what your muzzle blast is a rocket thruster! Again, the bullet does nothing beside provide a resistance to allow the pressure to build up!

If you knew as much about physics as you have claimed here at AR so many times in the past (don't feel left out you aren't the only clown that knows not of what you speak) then you could easily take the force versus time curves I have posted and calculate the REAL (read actual) recoil momentum, recoil velocity, and recoil energy.

In short the recoil numbers your website references come up with aren't as meaningful (read accurate) as the various penetration index and effect on game numbers (TKO).

ASS_CLOWN