Bullet Grains and Recoil

[Stanky626]

What's the correlation between the bullet grains and recoil? If I use a 9mm 147gr bullet, would that provide less recoil than a 9mm 115gr bullet? The velocity is noticeably higher in the 115gr vs 147gr.

[JagerDog]

mV^2/2

[highpower790]

more weight ,more recoil!

[Revoman]

The correlation between the grains and recoil is the law of physics, for every action, there is an equal reaction. If you're pushing out a heavier bullet that law indicates that there is more recoil, given the fact that other parts are equal such as velocity and weight of the firearm are equal and are shot from a rest for instance.
There are other recoil changing issues such as powder, slow burn, versus fast burn, high velocity versus low velocity to name two.
Technically, yes there is more recoil from a heavier bullet. Would you be able to tell the difference? Perhaps, but probably not with only a 32 gr difference.

[CSACANNONEER]

It depends on the muzzle velocities of the loads.

[sl0re10]

more weight ,more recoil!

This +1.

When you push on stuff; it pushes back. re: the reason a wall doesn't fall over when you push on it is because it pushes back...

push a bullet; it pushes back. Push a heavier one...

[JMP]

Energy is proportional to the square of the velocity and proportional to mass.
Momentum is proportional to mass and velocity.

Unfortunately, propulsion does not lead to a linear system, so it's going to be dependent on other factors, specifically the charge and you'd need to understand the higher order derivatives of position, acceleration, jerk, hyperjerk, and so on.

Generally, less recoil is obtained in practice with heavier bullets at slow velocities.

[Lead Waster]

You were probably talking to a gamer.

In USPSA, they have the idea of a "power factor", which is actually a function of kinetic energy. So weight of the bullet (grains) times the velocity (ft/sec) then divide the number by 10000. This gives you "power factor".

OK, so to play the game, your ammo must meet a certain power floor (I think it's 125) for higher scoring, it has some other criteria, but also a higher PF is needed.

OK, so what gamers do is, they want the softest shooting, least recoiling load they can make. So how do you maintain the power factor floor? Say you load 115 gn bullets with a certain amount of powder to get a certain velocity which just gives you the power floor + some breathing room. Now if you load up a 147 gn bullet ... you can use LESS powder because you require less muzzle velocity to reach the same power factor.

SO ... given an equal power factor, you CAN LOAD 147 gn rounds to SLOWER velocities than 115 gn loads. So that's what they do, so THEIR 147 gn loads have less FELT recoil than 115 gn bullets.

Since the heavier bullet is moving slower (given a set power factor) it will not snap as much and the FELT recoil maybe be less. But as mentioned, there is the law of conservation of momentum.

I think if you loaded the same powder load under a 115 anf a 147, the 147 would give more recoil. But again, it's the load that counts and people don't use the same powder load for 115 than 147.


I think.

[Stanky626]

Thanks. Good information in here.

[Dark Mod]

typically speaking a heavier round will increase roll where a higher velocity round will increase rear push.

Think of several different rounds at different grain weights with the same muzzle energy.

The heavier rounds that are slower will have more twist and the lighter rounds that move faster will push backwards harder. They will all have the same recoil, just applied differently in the recoil spectrum.

You will almost NEVER notice twist because your hands are wrapped around the grip and its just plain not going to register the way rearward pressure registers. If recoil is a problem, its probably best to use slower velocity ammunition.

To visualize it, think of a 10 trillion grn projectile moving at 1 fps down your barrel, then think of a 1 grn projectile moving at 10 trillion fps down your barrel. the 10 trillion grn projectile will wrench the gun out of your hand, the 1 grn projectile will blow that gun back into your face.

[TomReloaded]

My 180gr .40 loads recoil less than factory 115gr 9mm.

Hotter ammo has more recoil.

[TimRB]

Thanks. Good information in here.

And, as usual, some bad. Momentum is conserved, and momentum is mass times velocity.

MV(stuff going forward) = MV(stuff going backward--recoil)

Tim

[stilly]

This whole thing about pushing back is for physics and bullets. Do not do it to people. I pushed a toddler down the slide at the park today. Well, it was the steeper part of the slide, with all the rungs...

He did not push back, but he did try to pull me with him.

[choo2x]

Here's an article that did the math and also measured recoil empirically using a ransom rest. This is why I shoot a heavier bullet at a slower speed. Both the math and empirical results make sense to me.

Shelton

[spamsucker]

here. You'll want something that you can use to calculate/predict what kind of free recoil energy you'll be experiencing.

recoil energy = (Velocity * ((bullet weight in grains/7000) + 1.75 * (Powder charge grains / 7000)))^2

Weapon inertia = 63.348 * Gun weight in lbs

free recoil = recoil energy / weapon inertia

http://en.wikipedia.org/wiki/Free_recoil has a nice discussion of it but there's a lot of math at the top. There's a pretty chart down the page about 3/5ths the way down.