slug weight vs recoil

[76shuvlinoff]

I can bet this has been explained before but I am not sure I grasp what I have read.

I have various handguns in various calibers: 9mm, 357/38, 40sw and 45acp.
I also have a .357/38 lever carbine. I could do my own research but this is cheaper.

For some reason I have always assumed that the heavier the slug the harder it is to push therefore the harder the recoil. It's that equal and opposite reaction thing that sticks in my head. However I have read various threads stating the lighter slug will give heavier recoil. I am not going to drag them up to make an example of them, or to embarrass myself, this is for my own info.

Which is it or is it really even noticeable? Does using the same charge but varying the bullet weight dramatically change recoil intensity?

Thanks,
Mark

 

[crushbup]

I always thought that a larger bullet would give more recoil because it required more of a charge, but now I'm second-guessing myself.

 

[GRIZ22]

Recoil is basically a function of the total ejected mass (bullet and powder) with a factor for velocity vs the weight of the gun . A full 357 mag in a J frame S&W is horrendous while the same round in a N frame is easily managed.

With everything else being equal a lighter bullet will give less recoil than a heavy bullet.

 

[Frank Ettin]

First, there's a difference between recoil energy and felt recoil.

Recoil energy is a precise, physical quantity that is a function of the weight (mass) of the bullet, the weight (mass) of the powder charge, the muzzle velocity of the bullet, the muzzle velocity of the powder gases, and the weight (mass) of the gun. If you have those quantities for a given load in a given gun, you can calculate the amount of recoil energy produced when that load is fired in that gun. And a heavy bullet will produce more recoil energy than a lighter bullet fired from the same gun at a comparable velocity.

Felt recoil is a subjective matter. It's how you experience the recoil, and it's really something that only you can decide for yourself.

In general, for example, a lighter, fast bullet may produce recoil energy comparable to that of a heavier, slower bullet. But the recoil energy of the load with the lighter bullet will be manifest in a shorter pulse (distributed over a shorter period of time), while that with the heavier bullet will be distributed over a longer period of time. Depending on how you, personally experience these two types of recoil pulses, one may seem greater to you than the other, even though they really have similar recoil energy.

If you're interested, you can calculate the recoil energy of a given load using the following formula:

WG = Weight of gun in pounds
WB = Weight of bullet in grains
WP = Weight of powder charge in grains
VB = Muzzle velocity of bullet in f/s
I = Interim number (Recoil Impulse in lb/sec)
VG = Recoil velocity of gun (f/s)
EG = Recoil energy of gun (ft lb)

I = [(WB * VB) + (WP * 4000)] / 225218

VG = 32.2 * (I / WG)

EG = (WG * VG * VG) / 64.4

This formula is quite similar to a formula for free recoil set out at http://en.wikipedia.org/wiki/Free_recoil, although I think that the formula from Wikipedia may be a little more precise based on what I've read in Hatcher's Notebook. The formula I've reproduced above, is from the Q&As at http://www.frfrogspad.com/miscella.htm (specifically the question about why some guns of the same caliber kick harder than others). John Schaefer (FrFrog) notes that, "..."4000" is the nominal velocity of the powder gases at the muzzle for commercial smokeless powder and the observed range is between 3700 and 4300 f/s. It is sometimes stated as 4700 in some sources but this is based on observations of artillery, not small arms...." The Wikipedia formula would use the actual powder gas velocity, which may not be readily available.

 

[s4s4u]

What he said!

 

[Loomis]

Weight of the firearm has a greater effect on PERCEIVED recoil than does the weight of the projectile. A lighter firearm kicks harder than a heavy one does, if shooting the same ammo in both guns.

I will use the term "kicks" instead of recoil because there is a difference between how much it hurts you, versus what the mathematical value of the energy slammed into your body when you pull the trigger is. Just because it hurts your shoulder more, doesn't mean the theoretical recoil is greater...capiche?

Anyone that has reloaded ammo knows that a heavier bullet kicks less than a lighter bullet...I mean the lighter bullet hurts your shoulder more. But that is only true if you are using the same rifle for both ammo loads and both ammo loads are loaded up to the same chamber pressure.

Or, you can think of it this way...speedy bullets hurt your shoulder more than heavy bullets when fired FROM THE SAME RIFLE.

But, if you are loading two different batches of ammo, and one batch is a light bullet, and one batch is a heavy bullet, and you give them powder charges such that the heavy and the light bullets shoot THE SAME VELOCITY...then the heavy bullet will kick more than the light bullet.

So, in conclusion:
The people that tell you heavy bullets kick more than light bullets are telling you the truth. The people that tell you light bullets kick more than heavy bullets are telling you the truth. Both people are correct. Why? Because some people reload their own ammo and alway load them with the maximum safe chamber pressure allowed. When doing this, they will experience harder kicks from their rifle when shooting the lighter bullets. The people that tell you heavy bullets produce greater recoil than light bullets are telling you this because they have a rudimentary understanding of kinetic engery and newton's laws of motion. They understand that a heavier bullet travelling at X feet per second will transfer more energy into your shoulder than a light bullet traveling at the same feet per second.

 

[76shuvlinoff]

Thanks all, I think I "get it" now.