Via email from Jordan P. we have this RIFLE RECOIL TABLE. This is just part of the description:
The following chart provides a rifle’s recoil level
based on its recoil score*.
RECOIL SCORE* RECOIL LEVEL 1-2 Low Recoil 3-4 Moderate Recoil 5-10 High Recoil
The following table provides rifle recoil energy,
recoil velocity and recoil score of various rifle cartridges based on respective
projectile weight, projectile velocity, powder charge and rifle
If I had the time right now I would build and post a web app on Modern Ballistics for you to supply your own parameters and get the results for your exact situations.
I’m not sure that I believe the simple numbers in that table. There doesn’t appear to be any differentiation between rifle actions, and it makes a very significant difference in perceived recoil.
I shoot a couple of different rifles, bolt-action, in .30-06. I also have an M1 Garand in the same caliber. Shooting the same 150 grain ammunition through the bolt guns is fine, as long as I’m wearing a recoil pad and limit myself to 20 or 30 rounds. On the other hand, shooting with the semi-auto action of the Garand I can shoot for hours, even with a steel buttplate, without noticing the recoil.
While at about 5/8’s the recoil energy the same thing occurs when shooting 7.62×39 through my wife’s deer rifle (a bolt-action CZ), which has a much higher perceived recoil than shooting the same ammunition through any of the semi-autos, including SKS’s and AK’s.
Did I miss something in the table?
I don’t think you misunderstood anything. The table results were based on calculations which are only valid for blot, lever-action, pump, etc. without a muzzle break. The calculations for auto/semi-auto guns get very complicated and you need to know things like the mass of the moving parts the spring constant(s), how much gas (and its velocity) is returned in the gas tube and piston. Then you can make things almost impossible to model when you put a muzzle break on it.
The table definitely should have listed the gun used to get these measurements. The mass of the gun affects both the recoil energy and the recoil velocity; as an extreme example, if you jury-rigged an M1 Garand for full-auto it would be uncontrollable, but the BAR was controllable because it was about twice the mass. (However, I get the impression that it became a b***h to carry after a few hours marching and _not_ shooting.) So I think this table works at all mainly because most guns for similar cartridges are within 10% of the same weight.
Any energy diverted by the gun from propelling the bullet will reduce these numbers, but I would expect the typical self-loading action to only affect them a few percent – otherwise when the Springfield 03 was replaced by the M1 Garand, troops would have complained about a reduced range.
Finally, perceived recoil and actual measured recoil are not the same. The recoil energy and velocity in this table are integrated over an interval of time, so a stretched out “push” may measure the same as a sudden impact. They don’t _feel_ the same at all.
It is fascinating in a rather “side-bar-ish” sort of way. Obviously the muzzle energy is going to be a major indicator, but of course there are other factors.
This reminds me of the response I gave my son years ago when he asserted the old wives’ tale that says, “Rockets can’t work in a vacuum because there’s no air for the exhaust to push against”. (Someone had got to him with the whole “space is fake” business)
He was already familiar with rifle shooting so I used the example of a rifle’s recoil. He already (somewhat) understood “for every action there’s an equal and opposite reaction” and of course he felt it every time he fired a gun. “You think a gun isn’t going to recoil in a vacuum?” We therefore took the common foot pounds energy calculation for firearms and applied it to the expenditure of x grains of rocket fuel per second at y exhaust velocity, which yields z foot pounds per second. Bingo. Rockets work in space. QED