Formulas for recoil energy??

[socalbeachbum]

I see listings for muzzle energy for various calibers and loads. But the recoil I witness makes it seem like handguns don't follow Newton's 3rd Law of Physics about equal and opposite reaction. Which of course would be impossible.

Why do loads I'm using in my 25 oz 9mm marked 356 ft-lbs muzzle energy feel so much nicer than .45ACP marked 352 ft-lbs in a 38 oz pistol?

Do the known formulas for recoil enlighten us on this?

 

[Longhorn 76]

Foot-pounds is a measure of work, not energy, I think.

Recoil impulse probably has a time element involved.

 

[socalbeachbum]

if I remember right, foot-pounds would be force. then with a time element, like foot-lbs per second, it becomes work.

my confusion is mainly over not being able to really go by muzzle energy figures entirely as to how much recoil you are going to feel.

 

[Jim Watson]

Recoil is computed as a momentum balance. Muzzle energy of the bullet does not enter into it.

Mass of bullet times muzzle velocity plus mass of powder times powder gas jet velocity equals mass of gun times recoil velocity of gun.
You can then figure gun recoil energy as .5 times gun mass times gun velocity squared.

There are www plug in calculators all over.
One at
https://www.google.com/search?q=recoil+calculator+handgun&ie=UTF-8&oe=UTF-8&hl=en&client=safari
Which includes impulse as well as velocity and energy.

 

[rcmodel]

Here is another one:

http://www.handloads.com/calc/recoil.asp

rc

 

[481]

I see listings for muzzle energy for various calibers and loads. But the recoil I witness makes it seem like handguns don't follow Newton's 3rd Law of Physics about equal and opposite reaction. Which of course would be impossible.

Why do loads I'm using in my 25 oz 9mm marked 356 ft-lbs muzzle energy feel so much nicer than .45ACP marked 352 ft-lbs in a 38 oz pistol?

Do the known formulas for recoil enlighten us on this?

For total recoil they do- perceived recoil is a whole different beast.

For those with a DIY attitude-

where

M = bullet weight in grains
V = bullet velocity in feet per second
P = propellant weight in grains
W = firearm weight in pounds

[(MV + 4400P) ÷ 7000]² ÷ [64.34809711] ÷ [W] = Recoil Energy in foot-pounds

 

[Black Butte]

if I remember right, foot-pounds would be force. then with a time element, like foot-lbs per second, it becomes work.

Pounds is already a unit of force. If you multiply in distance, you get work, which equals a change in energy. Therefore, a foot-pound is a unit of both work and energy.

 

[jmr40]

If you want to figure "ACTUAL" recoil just use one of the online programs and plug in the numbers. I use the one RC linked to. No point in doing complicated math when these online programs are available.

"FELT" recoil is a bit different, is different to different people and almost impossible to define. A handgun like a Glock 21 with their fat grips and sharp grip angle really soften reciol considerably compared to a heavier 1911 with its very narrow straight grip. Even though the Glock is lighter, the recoil is spread out over a larger portion of your hand and there is much less muzzle flip to compensate for.

With rifles and shotguns you get the same effect with fat vs skinny butt plates/recoil pads. A long gun that fits my body shape may be far more comfortable to me to shoot than someone else with longer/shorter arms, a thicker/thinner face, thicker/thinner chest etc.

To me most lever action 30-30's hurt much more than my bolt rifles in 308 even though the "ACTUAL" recoil numbers are much higher. It is because of the stock design and lack of recoil pads on 30-30's

A Lot of felt recoil is really between the ears. Lots of guys are convinced anything with magnum in the name is going to kick. They believe it before they pull the trigger, and to them it is really bad. In reality a great many standard rounds recoil much more than rounds such as 7mm and 300 magnums. Muzzle blast and muzzle flip have a way of tricking our brains. A louder gun or one that has a lot of muzzle flip seem to recoil more even though they don't.

It could be that in your mind a 45 is supposed to have a lot more recoil than a wimpy 9mm. In your guns it doesn't, but if you believe it before you pull the trigger you will think it does.

The 1st handgun my wife ever fired was a 41 magnum. She asked me if it recoiled a lot. I told her no, she believed me and it didn't. She still believes a 41 magnum is light recoiling and any magnum handgun round has never bothered her.

 

[1911Tuner]

But the recoil I witness makes it seem like handguns don't follow Newton's 3rd Law of Physics

But they must. They're Newton's Laws...not Newton's Theories.

Recoil is force...acceleration...and momentum.

Momentums are equal. That is, the reaction side's momentum is equal to the action side's momentum.

And force forward=force backward.

The rate of acceleration...or the recoil impulse...isn't equal. The bullet accelerates much faster than the gun. A full-throttle 158-grain .357 Magnum fired in an N-Frame 6-inch Model 27 doesn't punch your hand as hard as the same round fired in a 3-inch K-Frame Model 13.

Recoil is only present as long as the bullet is present and being accelerated. When the bullet exits, recoil is over...and any further movement of the gun AND the bullet are accomplished as a result of momentum imparted during acceleration.

Most of what we perceive as recoil is momentum...and the larger/heavier gun doesn't seem to recoil as much, even though the momentums are equal. It only seems that way because the greater mass doesn't accelerate as rapidly as the lower mass.

As noted, felt, or perceived recoil is modified by stock design. Install a large set of target stocks on the Model 13, and it won't be at all unpleasant. Shoot it with the small service "Magna" stocks...and it'll sting your hand.

 

[socalbeachbum]

thanks guys. the results outputs from the calculators make perfect sense. a fun way to look at handgun selections too.

I watch guys like Miculek rip 6 shots of 45ACP or 38 Super in under 2 seconds, and wonder how light a load he uses. seems in a revolver you can load pretty light.

I understand about calculated vs felt, I have a simple grip sleeve on my plastic Glock 19 and recoil feels like nothing. I have hard plastic Crimson Trace grips on my S&W 60 and firing .38 spcl, the hand gets beat after a while.

thanks for the great answers.

 

[1911Tuner]

I understand about calculated vs felt, I have a simple grip sleeve on my plastic Glock 19 and recoil feels like nothing. I have hard plastic Crimson Trace grips on my S&W 60 and firing .38 spcl, the hand gets beat after a while.

There's a problem with comparing a revolver with an autopistol.

With a fixed breech weapon...the revolver...the acceleration/impulse is transferred immediately and directly to the frame. With the auto, the only connection between the frame and the breechblock...the slide...is through a spring. Most of what you perceive as recoil actually comes from the slide impacting the frame. By the time that happens, recoil from the action/reaction event that comes from firing the cartridge is over because the bullet is long gone. As an example...using a standard velocity 230-grain .45 round...by the time the slide hits the frame, the bullet will hit a target some 20 yards away.

 

[socalbeachbum]

right.

so... I wonder what % recoil reduction there is in a 'typical' auto pistol?

I fired a PX4 a few days ago and the recoil felt pretty light, and I know Beretta claims that as the barrel rotates, energy is dissipated radially, which I don't really get.

 

[1911Tuner]

so... I wonder what % recoil reduction there is in a 'typical' auto pistol?

Assuming equal ammunition...none. Recoil is the reaction side of an action/reaction event. Forces are equal. Momentums are equal. You can only change how you feel it...or maybe how you absorb it would be more accurate.

Revolver vs Auto boils down to a sharp punch vs a fast push with a sudden snap at the end as the slide hits the frame.

Increase the frame mass in the revolver, and the punch is a little slower...but the momentum is equal.

Increase the spring rate in the auto, and the push is a little sharper because force forward is force backward. The spring pushes harder forward on the slide...and harder backward on the frame. The sudden snap at the end is diminished a little, but the sharper push compensates for it.

But with a given cartridge/bullet weight/velocity/acceleration rate...momentums on the reaction side are equal.

 

[wally]

After watching new shooters shoot suppressed I think muzzle blast is a big part of perceived recoil.

My friend's daughter had never shot a real gun before so we started her off with a Ruger 22/45 and she was a natural hitting the larger steel plates essentially 100% once she got used the sights. Later we let her shoot my suppressed M&P 9. It was a bit heavy for her, so her hold was a tad unsteady, but what was interesting was when she missed I could see the gun recoil, but she barely reacted to it, but whenever she hit the steel its loud "ring" made her "jump" every time like she had fired a "big gun"

 

[socalbeachbum]

do compensators, muzzle brakes, or magnaports decrease recoil, but increase muzzle blast?

 

[rcmodel]

Yes.

Actually, the recoil is still there, but redirected so it feels lighter.

rc

 

[Jim Watson]

I think in some degree, the recoil is gone.
Part of the recoil is a jet effect from the powder gases squirting out after the bullet uncorks the barrel. If a compensator can direct some of those gases laterally, their component of recoil is gone. It is enough for a fast shooter to tell with a racegun firing a light bullet at high velocity with a large for pistol powder charge. It can be very noticeable in a rifle if you can get any good part of the gas which can mass more than half the bullet weight to go sideways.

But the blast is amplified, which can be very disturbing.
Yes, I think blast acts as a component of felt recoil. I prefer 147 gr 9mm subsonics for IDPA; like shooting a 10-shot .38 Special. My last purchase of bullets under The Panic, I settled for 125s. I was pleasantly surprised that they were not nearly as nasty to shoot as 115 gr econo-ball. But the 125s, loaded to 1903 DWM ballistics of 1040 fps are subsonic and conventional 115s are supersonic with a bit more powder and a hard Crack!

 

[socalbeachbum]

so those linear compensators they have come up with direct the gases forward, but I guess act as a diffuser giving you less jet effect? like opening and closing the nozzle on an afterburner, reducing or increasing thrust

 

[Jim Watson]

A friend bought one trying to get something for nothing.
And nothing is mostly what it does.

 

[BlindJustice]

Interesting thread

I used the Recoil calculator RCmodel gave a link to

I put in the loads for 45 AP and 9x19 I shoot
in a full size 1911 and a CZ 75B, when they are each fully
loaded they are near the same wight

45 ACP/9x19
-- 230 -- 124
-- 890 --- 1175
7.0 --- 6.0 <--- best guess of Unique
Calculates to
---- 1.03 <-> 0.75 Recoil Impulse (Lbs sec)
--- 13.57 <-> 9.90 Velocity of recoiling firearm(FPS)
---- 7.00 <-> 3.72 Free Recoil Energy (Ft Lbs )


Why isn't barrel length an input in this cacluation?

It's interesting to compare the same load in
a steel frame 1911 vs an alum frame full size, about 1/2 poiund

or the recoil calculated for A. a full magazine vs only one round left to fire
a full 8 rd mag of 230 gr. is a bit over 1/2 pound

R-


R-

 

[BlindJustice]

1811Tuner

There's a problem with comparing a revolver with an autopistol.

With a fixed breech weapon...the revolver...the acceleration/impulse is transferred immediately and directly to the frame. With the auto, the only connection between the frame and the breechblock...the slide...is through a spring. Most of what you perceive as recoil actually comes from the slide impacting the frame. By the time that happens, recoil from the action/reaction event that comes from firing the cartridge is over because the bullet is long gone. As an example...using a standard velocity 230-grain .45 round...by the time the slide hits the frame, the bullet will hit a target some 20 yards away.

****

If the recoil is muted by the reoil spring
and delayed until the slide hits the frame
Shouldn't the weight of the slide be there
in a clac. for that sudden stop?

Randall

 

[BlindJustice]

Being a regular at the range with my
S&W Model 60 3" bbl. adj. rear sight/ 225 oz empty

I used the recoil calculator to see how much difference there is
from light .38 special up through .357 Mag.

38 Spcl +P +P 57 Magnum
148 g. 125 gr. 158 gr. 125 gr. 158 gr. 125 gr 158 gr.
LWC TMJ-FN RNL JHP JHP JHP JHP
Feet per sec.@ 759 @ 865 @ 755 @ 950 @ 850 @1,450 @1,240
Recoil Impulse
-- ( Lbs sec. ) 0.63 0.62 0.67 0.67 0.74 0.98 1.05
Recoil Vel.fps 12.21 12.07 13.03 13.1 14.44 19.07 20481
Recoil energy: 3.82 3.83 4.38 4.4 5.34 932 10.75

Quite a range

R-

 

[socalbeachbum]

hey blind, I just got a SW Pro series 60 3" and LOVE it! very accurate!

 

[1911Tuner]

BlindJustice asked:

If the recoil is muted by the reoil spring
and delayed until the slide hits the frame
Shouldn't the weight of the slide be there
in a clac. for that sudden stop?

The weight of the slide times its velocity at time of impact is expressed as momentum...and the momentum is equal to the bullet's. Actually a bit less, but it's close enough that we can call it equal. It can be less, but it can't be more. Switch to a shorter/lighter/faster slide, and the impact momentum is still equal to the bullet's, even though it's traveling a little faster.

Look at this old fluroscope photograph closely. It catches the gun just after the point of maximum acceleration on the slide...recoil. The slide has moved about .075 inch here. If you look closely, you can see the bones in the shooter's hand. Among other things that it reveals is that the gun has moved very little, if any, during the action/reaction phase that comes from firing the cartridge.

What little it does move is provided by the spring's bearing forward on the slide and backward on the frame. The recoil spring becomes a vectored force between two interacting objects...or a separate action/reaction system that's independent from the ballistic event.

Extreme slow motion videos also bear this out. The gun moves very little until the slide hits the frame...and then it's jerked violently upward...or what we recognize as muzzle flip.

 

[brickeyee]

You use conservation of momentum for the ejecta (powder & bullet and their respective velocities) and the gun, then apply 1/2 mv^2 to the momentum of the gun.

This does ot account forthe speed of the movement.

The more complicated impulse calculation does that, but there is often enough difference in perceived recoil to make the impulse method needlessly complicated.