None of the classic recoil calculations mean much. We use them because they are simple to do, not because they give much in the way of useful information.
Our bodies perceive pressure (force per unit area), not momentum. And the actual circumstances of a fired firearm are nothing like the assumptions that the recoil calculation requires.
Another way to think of impulse is the force felt over a certain period of time, which is the same as the change in momentum.
An easy way to visualize this is if you picture a car accident. Old cars that were solid steel went from 30mph to 0mph in a very short amount of time when they crashed. The car going from 30 to 0 has a certain amount of momentum associated with it, and the shorter the amount of time in which that momentum change takes place, the great the amount of force felt. This means that you felt a great amount of force across your shoulder and lap from your seat belt. Newer cars are designed with crumple zones, which are there to maximize the amount of time that it takes the car to go from 30mph to 0mph, and when you increase the amount of time, you decrease the felt force on your body from your seat belt. The change in momentum is the same, as long as the cars weigh the same, since they're both going from 30 to 0 mph, but the newer car takes longer to come to a complete stop.
The same applies to your shoulder, given a constant recoil pad size, in that the less time it takes for the the rifle to reach its maximum recoil velocity, the greater the force you feel.
the recoil impulse is more or less what im most concerned with in a bigger rifle...the quick impulse of something like a fast 375 in a light rifle [bleep] sucks as it likes to try and stretch the ligaments in my shoulder to their snapping point.....however take something like a 458 in a sane weight that has the same recoil energy of that fast 375 and it wont be as big of a deal cause the recoil impulse is more like a hard push than a hard jab....it doesnt feel near as bad....
the ft-lbs of recoil on both rifles may be identical but the recoil impulse difference is what makes one a beast and the other tolerable....
A mass accelerated at 500 g for 1 millisecond (about what you get out of a 30-06) will have the same final speed and will have the same change in momentum (impulse) as the same mass accelerated at 1 g for 500 milliseconds. I guarantee that the two feel completely different.
The classic calculations require that the firearm be freely recoiling. A shoulder fired rifle or hand held handgun is far, far from being freely recoiling. The calculations soundly violate the required assumption.
I've talked before on here about an 8mm Rem Mag that I used to own. The raw numbers would suggest that it shouldn't be too bad. But because the recoil was so fast and "sharp", the recoil was flat nasty.
A 375 H&H, firing bullets 100 grains heavier, was downright docile compared to it, due to the slower recoil impulse.
A sharp jab vs a big push is the easiest way to describe it.
Both were practically identical M700's, in Classic stocks, so it was a pretty even comparison.
The term "felt recoil" applies as the raw number often poorly represents a dynamic that varies widely in the recoil experienced. Stock and recoil pad design are a big deal (variable) here, in addition to previously mentioned factors.
Recoil Energy is meaningless. What recoils is the Impulse. Impulse=Momentum The Mass x .the Velocity = The Force x Times the time it applied. The force on the butt plate is recoil. How long it applied depends on several things. A recoil pad stretches the time out which reduces the force. There is another term Jerk which is the the rate of change in acceleration. That is why in some guns the Muzzle blast adds another push. Newton only spoke to Conservation of Momentum not Energy. It's all in a basic Physice Book.
Arthur Pejsa's free recoil formula gives powder weight more importance than bullet weight, which suggests a lower recoil benefit from using powders that give the needed bullet velocity with the least charge weight. Free recoil is in direct proportion to gun weight. You can see this for yourself using any competent recoil calculator. As an experiment enter double the gun weight and you'll get half the recoil energy for the same load.
Beyond gun weight and load particulars, I believe stock design has a lot to do with how recoil is felt. Guns that are designed to avoid barrel rise (stock in-line with the barrel as on an AR-15) are going to have greater felt recoil for a given load than those that are designed to dissipate recoil energy by rotating the rifle barrel up.
Another factor is the action, with gas operated actions having less felt recoil than a bolt action due to the gas operated action acting in the opposite direction. The free recoil energy is the same, but the forces are spread out over a longer time, which reduces the peak force being felt by the shooter. That's the same way a recoil pad works.
...I believe stock design has a lot to do with how recoil is felt. Guns that are designed to avoid barrel rise (stock in-line with the barrel as on an AR-15) are going to have greater felt recoil for a given load than those that are designed to dissipate recoil energy by rotating the rifle barrel up.
I disagree. I would much rather take the recoil straight back in to my shoulder, as opposed to up into my face and head.
...I believe stock design has a lot to do with how recoil is felt. Guns that are designed to avoid barrel rise (stock in-line with the barrel as on an AR-15) are going to have greater felt recoil for a given load than those that are designed to dissipate recoil energy by rotating the rifle barrel up.
I disagree. I would much rather take the recoil straight back in to my shoulder, as opposed to up into my face and head.
depends on build.....for me a straight line stock is the best, i prefer it by far to anything else.....however they tend to beat my wife up in anything but the lightest rounds cause how she has to contort to use them....
Obviously personal preference comes into play, and with less energetic calibers an in-line stock has its advantages such as getting the sight picture back quickly. Once you start throwing 300 grains or more downrange I find a more traditional stock has the advantage assuming I use the proper technique of rotating with the rifle as one or two shooters in this video demonstrate.
This has been posted before, but it sure shows recoil results of using heavier bullets.
I made a fancy looking recoil slide for testing recoil of rifles with different weights of bullets and with different brakes installed. I put a chronograph just past the slide. On July 15, 2007 I tested a few rifles.
Here are enough to get an idea how different weights of bullets affect free recoil travel. Which translates into usable information.
No brake .223 26� heavy barrel 55 grain moly 3,306 feet per second 1 13/16� .223 22� light barrel same ammo 3,260 2 3/8� .223 22� light barrel 60 grain 3,118 3 1/8�
7 Rem Mag 120 grain 3,380 12 7/8� 7 Rem Mag 140 3,027 15 5/16� 7 Rem Mag 170 2,852 19 15/16� 7STW 130 3,763 15 1/8� .375.-416 Rem Mag 270 2,968 29 �� .375-.416 Rem Mag 300 2,858 35 11/16�
Factory brake with large chamber 7 Rem Mag 120 grain 3,419 7 ��
