Need help with the causes of recoil.

[richardraw316]

Sorry guys, to most of you this may seem obvious, but not to me.
I am trying to wrap my mind around what recoil is.
newton states for every action their is an equal and opposite reaction.
so going just by that theory, a 40 S&W delivers 500 ft-lbf of energy at the muzzle,(yes this is a very hot round.) then the person firing the weapon should feel the same energy in their hands.
so the higher the muzzle energy is directly affecting percieved recoil.
I understand their are alot of variables to figure in. barrel length, weight of weapon, and even grip type all affect recoil. but is this formula correct?
Is muzzle energy, going to give me a good indication of recoil?
i have never shot an AR-15, so i really dont know personally, but most people think that 5.56 is a rather light recoiling round. of course this is a rifle, and thus absorbs more energy, but what if you tried different ammo in similar rifles? 5.56 1700 ft lbs of energy. 30-30 around 1700 ft lbs of energy and i was told rather stout recoil.
is there something i am missing.
thanks for your help guys, on my quest for knowledge.


ps. after reading my post i relized for my example i am comparing semi auto against a lever action. this of course would directly affect recoil, so change the AR to a bolt action that fires 5.56, and that would be a better comparison.

 

[phylodog]

Semi automatic weapons absorb or re-utilize a good bit of the recoil energy to function the weapon. An AR15 has a nice big spring being pushed back by a relatively heavy bolt carrier group. A 30-30 transmits the recoil energy into a fixed breech face which pushes it into the shoulder.

 

[threefiftyfour]

recoil springs

 

[richardraw316]

sorry guys i was editing when you posted.

 

[NIFT]

Newton's Third Law says in an inertial reference frame, for every force there is an equal and opposite force.

Neither energy nor kinetic energy are forces. Kinetic energy is a mathematical construct.

Often overlooked in Newton's Third Law is that forces must occur in pairs; there can be no single, isolated force.

Also, Newton's First Law establishes the definition of an inertial reference frame:
In an inertial reference frame, a body will remain at rest or in constant motion unless acted upon by an outside force.

 

[rugertoter]

There is a formula for figuring the opposite reaction called recoil, but I would have to find it in my stack of gun books. Google it I guess, but none the less you have to consider a few things. One is the weight of the weapon. Another thing is the mechanical action of the gun itself helps to dissipate some of the recoil. Also, just because the bullet impacts with a certain amount of force, does not mean that it requires that much force, in foot pounds, to push it out of the barrel. If I can find that formula, I will post it for you. (Physics is not my strong point)

 

[NIFT]

The pound is the English unit of force. Foot pounds is a unit of work.

 

[richardraw316]

if we could make all things equal.
say a big revolver, 500 mag. 3000 ft lbs of energy
same revolver, 7.62x54r. 3800 ft lbs of energy
by these number alone. the rifle round recoils harder. is this correct?
i know they do not make a revolver that shoots that round, but someone should.

 

[rugertoter]

The pound is the English unit of force. Foot pounds is a unit of work.

Like I said, Physics is not my strong point, but I read about that formula just a couple of months ago. I will search through my stack and see if I can find it. Like finding a needle in a stack of needles.

 

[MTC]

The pound is the English unit of force.

And here I thought the King's Regiment of Foot was the (primary) English unit of force.

Seriously, though, thanks for the review.

 

[NIFT]

Like I said, Physics is not my strong point, but I read about that formula just a couple of months ago. I will search through my stack and see if I can find it. Like finding a needle in a stack of needles.

There are equations for figuring "free recoil energy" whatever that is, and you can plug in the gun weight, projectile weight, and powder charge, to get a result.

However, powder charges of the same weight do not all have the same "power." Plus, factors such as the gun's action, size and material of the grip, recoil pad (long gun), and so on all affect felt recoil, which, in the end, is somewhat subjective.

Basically, other things equal (!), lighter guns, heavier projectiles, and heavier charges "kick" more than heavier guns with lighter bullets and lighter charges.

 

[neraph]

It's momentum that is conserved in the system, not kinetic energy.

Thus, a 55gr bullet at 3000 fps will recoil the same as a 165gr bullet at 1000 fps if fired from the same gun using the same amount of powder. The momentum of the escaping gases results in recoil as well, which is why the same bullet travelling at the same speed will recoil differently using different powders.

However, momentum is not directly experienced by us, but the velocity and energy of the firearm. Here's a calculator if you want to play around:
Recoil Calculator

 

[richardraw316]

side note. anybody have the formula for figuring ft lbs of energy base on speed of prjectile and weight of projectile. always wondered the equation on that one.

 

[NIFT]

It's momentum that is conserved in the system, not kinetic energy.

Thus, a 55gr bullet at 3000 fps will recoil the same as a 165gr bullet at 1000 fps if fired from the same gun using the same amount of powder. The momentum of the escaping gases results in recoil as well, which is why the same bullet travelling at the same speed will recoil differently using different powders.

However, momentum is not directly experienced by us, but the velocity and energy of the firearm. Here's a calculator if you want to play around:
Recoil Calculator

That's it!
However, remember, there are many other factors--the gun's action, grip size and composiition, recoil pad (long gun), etc.--that affect felt recoil.

 

[hammer24]

Joules are the unit of energy. Joules can be converted to ft./lbs. of force (ft·lbf).

Calculating free Recoil using non-SI units
From the momentum long form in both Imperial units of measure and in an English Engineering format:

• Momentum long form:
  
  →
  

Where as:
Etgu is the translational kinetic energy of the small arm as expressed by the foot-pound force (ft·lbf).
mgu is the weight of the small arm expressed in pounds (lb).
mp is the weight of the projectile expressed in grains (gr).
mc is the weight of the powder charge expressed in grains (gr).
vgu is the velocity of the small arm expressed in feet per second (ft/s).
vp is the velocity of the projectile expressed in feet per second (ft/s).
vc is the velocity of the powder charge expressed in feet per second (ft/s).
gc is the dimensional constant and is the numeral coefficient of 32.1739
7000 is the conversion factor to set the equation equal to pounds

 

[hammer24]

I use the calculators at http://www.handloads.com/. I don't like physics enough to do it in my spare time!

 

[netsecurity]

It makes sense to me. If the force is enough to bump a heavy rifle into your shoulder, just imagine that same equal force pushing a tiny piece of lead. Heavier grain bullets have more recoil.

Asides from the aforementioned automatic mechanisms using some of the energy, the main factor in recoil is the weight of the gun. A heavy gun can feel like almost no recoil at all, even with a large bullet. A light gun like the AR15 relies on a very small bullet, as well as the buffer spring to minimize recoil, and is an excellent design.

 

[richardraw316]

Joules are the unit of energy. Joules can be converted to ft./lbs. of force (ft·lbf).

Calculating free Recoil using non-SI units

From the momentum long form in both Imperial units of measure and in an English Engineering format:

• Momentum long form:
  
  →
  

Where as:
Etgu is the translational kinetic energy of the small arm as expressed by the foot-pound force (ft·lbf).
mgu is the weight of the small arm expressed in pounds (lb).
mp is the weight of the projectile expressed in grains (gr).
mc is the weight of the powder charge expressed in grains (gr).
vgu is the velocity of the small arm expressed in feet per second (ft/s).
vp is the velocity of the projectile expressed in feet per second (ft/s).
vc is the velocity of the powder charge expressed in feet per second (ft/s).
gc is the dimensional constant and is the numeral coefficient of 32.1739
7000 is the conversion factor to set the equation equal to pounds

now i feel really stupid.
physics suck.

 

[echoagain]

Yup, what neraph said...

Momentum is a fairly simple concept, it is simply mass (weight for practical purposes) x velocity. When a bullet is fired, the momentum of the bullet going away (hopefully!) from you will have exactly the same quantity of momemtum as the firearm that is now traveling toward you.

Essentially, the powder charge is just separating two objects (the gun and the bullet) and imparting an equal and opposite momentum to each. For any given bullet weight, the faster you launch it, the greater momentum that is generated in both it, and in the firearm. Momentum is momentum, but how this momentum is perceived by the shooter is a different animal. In general, the heavier the firearm, the less the 'kick' is perceived by the shooter, even though the actual momentum is the same. Other factors such as the geometry or action of the weapon, materials and even differences between shooters all 'muddy the water' as far as this idea of 'perceived' recoil.

Loads and cartridges with higher energies will typically have greater recoils, or momentums. But, energy is a function of the square of the velocity, so this is not always mathematically true. In other words, recoil is not directly proportional to the energy levels.

 

[sloughfoot]

Newton's Third Law says in an inertial reference frame, for every force there is an equal and opposite force.

Neither energy nor kinetic energy are forces. Kinetic energy is a mathematical construct.

Often overlooked in Newton's Third Law is that forces must occur in pairs; there can be no single, isolated force.

Also, Newton's First Law establishes the definition of an inertial reference frame:
In an inertial reference frame, a body will remain at rest or in constant motion unless acted upon by an outside force.

This is why you are one of my favorite people on this planet.

Your comment on "felt recoil" brings up the point that many things can change how much recoil is felt by the shooter. Even the angle of the buttplate can change how the recoil feels to the shooter.

That is my layman's opinion. I will now go back to reading what you smart guys say about the subject.