Bullet weight effect on recoil?

[Kiwi cop]

I have always understood that a heavier bullet will recoil more in a gun than a lighter bullet does as recoil is a result of both weight and velocity but with weight having a greater influence.

That was my understanding behind the 125/135 gn .357 Magnum being more controllable than a 158 gn bullet.

But yesterday I had someone with a lot of experience tell me (insist) that a lighter bullet recoils more because of the velocity. This person insisted that a 147 gn bullet in 9mm recoils less than a 124 gn bullet because it is going slower.

Which is right?

 

[shocker]

Conservation of momentum (recoil) vs. conservation of energy (ability of bullet to do work on the target) favors lighter bullets moving at higher velocity.

 

[murphydog]

Kinetic energy is 1/2 (mass) X (velocity) squared. So, increases in velocity have more effect on energy than mass. A heavier, slower bullet 'may' generate less energy than a lighter, faster bullet depending on how much slower, using the above equation.

However, recoil (how much perceived "kick" by the shooter) is also dependent on the gun used. A flyweight subcompact 9 mm will recoil much more than a steel 1911.

 

[ContinentalOp]

This is my understanding of how it works...

Take two loads with the same muzzle energy, a slow-heavy load and a light-fast load, fired by the same shooter from the same gun. They have the same energy, so the recoil energy would also be the same ("equal, but opposite...etc.").

The difference is in how that energy is perceived by the shooter. The slow-heavy bullet, being slow, takes longer to accelerate, so the recoil force the shooter feels will be more like a push, because that energy is delivered over a longer period of time (even if it's measured in fractions of a second). The light-fast bullet accelerates faster, so it will deliver it's recoil energy more quickly, and will feel like a snap.

I will freely admit I could be wrong, but it does seem to make sense to me based on experience.

 

[rockquarry]

With 9mm, not enough recoil difference to concern yourself with. Use something that shoots well for you; bullet weight is very secondary.

 

[CDR_Glock]

For a 9 mm in 115 gr going supersonic, there is more recoil felt, than from a heavier bullet going subsonic. But if we matched the energy and velocity, the heavier bullet would have more recoil.

158 grain and 180 grain 357 magnum have more recoil than 125 grain.

For a 500 magnum, there is more recoil in a heavier bullet weight of 500-700 grains versus 325 or 350 grain bullets.


Sent from my iPad using Tapatalk Pro

 

[BC38]

This is my understanding of how it works...

Take two loads with the same muzzle energy, a slow-heavy load and a light-fast load, fired by the same shooter from the same gun. They have the same energy, so the recoil energy would also be the same ("equal, but opposite...etc.").

The difference is in how that energy is perceived by the shooter. The slow-heavy bullet, being slow, takes longer to accelerate, so the recoil force the shooter feels will be more like a push, because that energy is delivered over a longer period of time (even if it's measured in fractions of a second). The light-fast bullet accelerates faster, so it will deliver it's recoil energy more quickly, and will feel like a snap.

I will freely admit I could be wrong, but it does seem to make sense to me based on experience.

^^^This is my understanding of how it works as well^^^
Physics is physics, and equal ME means equal forces, means equal amounts of work being done.
Work = mass moved over time.

A milder longer PUSH vs a sharper shorter SLAP
As a rule the heavier bullet will FEEL like it gives less recoil (a.k.a. less perceived recoil).

 

[torizus]

I'm all in with ContinentalOp & BC38, I always use the terms "push" vs "snap". I first realized it with the 45 Colt revolver and the 45 acp. auto. Always thought the 45 auto felt a bit snappier than the Colt revolver.

 

[Nevada Ed]

A larger weight bullet does not have to have more recoil if it is
slowed down.

I can load my 30-06 with a 180gr to shoot with the recoil of a 30/40 Krag or my .270 to have the recoil of a 257 Roberts.

Lots of my 9mm 124gr are the speed of a 4" 38 special.

However I am still young enough to enjoy full loads every now and then at the range, but that is with 6" heavy frame weapon
with the .357 in at least a L frame, to reduce the recoil.

The weight of the weapon plays a large part in how much recoil
you will receive with full loads.

Are you thinking of shooting .357 mags in an "Airweight" , to
see about control ??

I want pictures !!

 

[Big Cholla]

Continentalop stated the OP's answer correctly but I would like to clarify just a little......."Perceived Recoil" is what we are discussing, not muzzle velocity or muzzle energy. The factor of great importance to Perceived Recoil is the time taken by the bullet from ignition to exit of the barrel. A light bullet takes milliseconds less time than the heavier bullet. A heavier bullet is imparting heavier felt recoil all the time until leaving the barrel. With the same sight setting a heavy bullet will cause the muzzle to raise higher during recoil than the lighter bullet and usually causes the heavier bullet to strike the target higher than the lighter bullet. The sensation of recoil perceived by the shooter is longer for the heavier bullet. That translates to our hand, nerves and brain as "heavier" recoil. Usually, the heavier recoil causes the muzzle and the entire handgun to raise higher for the initial shooting position and will give longer times for recovery and re-aiming on subsequent shots. Once I figured that out I favored the lighter bullets in most calibers because of the desire to improve shot time between shots after the first shot. Of course the necessity to make all shots "hits" intensifies.

 

[Dave Lively]

If you look just at the bullet and gun conservation of momentum means the percentage of energy you feel as recoil is proportional to the total energy divided by the combined weight of the gun and bullet. For example if you have a 2 pound (14000 grain) revolver firing a 125 grain bullet generation 550 ft-lbs of energy the recoil energy would be 550 *125 / (14000 + 125) = 4.9 ft-lbs. The bullet would have 550 * 14000 / (14000 + 125) = 545. ft-lbs of energy. With a 158 grain bullet and the same energy level the recoil energy goes up to 6.1 ft-lbs.

But that math leaves out a lot of variables.

1 - Typically heavy bullet loads generate less energy. Speers 125 grain 357 gold dot is rate at 580 ft-lbs and their 158 grain Gold Dot is rated at 530. When you look at the difference in calibers like 9mm and 40 S&W where heavy bullets don't leave enough room for powder the difference is more pronounced.

2 - It doesn't include the effect of the powder. After the bullet exits the barrel the still burning powder acts like a rocket aimed into your hand. The more powder that remains after the bullet exits the greater this effect will be. The more pressure that remains the greater this effect will be. It is one of the reasons short barrelled guns have more recoil. It seems like heavy bullet loads burn more of the available powder and this factor favors heavy bullets.

3 - Perceived recoil can be affected by how loud a gun is. Maybe this one is just me but even with good hearing protection loud guns seem to have more recoil. This is entirely psychological so it is going to vary a lot from person to person. Light bullet loads tend to be louder.

4 - How tightly you hold the gun. When you firmly grip a handgun or pull a rifle tightly into your shoulder you add some of your body mass to the mass of the gun. Tightly held firearms don't just feel like they have less recoil, they actually HAVE less recoil.

5 - It doesn't take into account how the recoil impulse is spread out. A semiauto that spreads out the recoil energy is going to be less punishing than a revolver firing the same cartridge.

The engineer in me really wants there to be a simple mathematical formula for predicting recoil. But all the added variables I listed here and others I haven't thought of make that impossible. So I end up going with what I have learned from 30 years of shooting. With handguns ammo with light bullets being pushed as fast as possible will make me more likely to flinch than ammo with heavy bullets being pushed as fast as possible. With rifles the reverse is true. How likely I am to start flinching (or anticipating the shot as it is now called) is not the same as true recoil it is what matters most to me.

 

[Nevada Ed]

As for a 33oz. 9mm pistol's Recoil, per loads.......

115gr
1033fps R 2.88
1350 ........ 5.16 pf155

124gr
1024fps .... 3.28
1267 ......... 5.17 pf157

135gr
907fps ....... 2.95

147gr
890 ........... 3.32
1040 ......... 4.76 pf153

please note the difference in PF and recoil with the loads.

Later.

 

[HughD1]

The grips on the gun and how they affect your grip on the gun also can change the felt recoil considerably. Different grips can change the amount of area receiving the blow and if the force is coming straight back or going in to muzzle rise.

 

[Joe4d]

At equal flt lbs recoil will be about the same,
At equal power factor.. ( straight mass X velocity) heavier bullet will recoil less, assuming same powder charge.
In the same gun, perceived recoil is a factor of bullet weight, powder weight, and powder burn rate. I honestly dont think velocity matters,, as its basically a function of powder weight and burn rate.
Slower powders produce more muzzle jet action and use heavier charges to reach the same velocities, yet produce more recoil..
Just shoot a 9mm 125 light charge of fast powder in a compact 9mm against a 125 gr 357 magnum in a snubby.
Same work, same bullet mass, grossly different recoils.
So really you cant say, "Heavier bullets recoil less or more" both statements would be wrong without taking into consideration other factors.

 

[BC38]

I think we're getting way off into the weeds here.

Obviously if you change from a revolver to a semi-auto it is going to make a difference. So will changing grips, or firearm weight, or barrel length, or powder burn rate, or any number of other factors.

The question (and the point) is with all else being EQUAL, will a heavier bullet propelled by a smaller charge or a lighter bullet propelled by a larger charge give more recoil?

If the PF and ME are the same the amount of recoil energy will be the same. The PERCEIVED recoil may very well be different since the light bullet with its larger charge of powder, and it's corresponding higher velocity, will cause the recoil pulse to be shorter, sharper, and therefore FEEL more violent.

Kind of like comparing someone giving you a hard PUSH against your cheek vs. them SLAPPING you on the cheek. Both may have the same energy and move your head the same distance, but the slap will hurt more and that will make it seem more violent. That's how I see the difference in perceived recoil.

Since no one (except maybe Ed ) measures recoil with instruments, most of us only have the recoil we feel (perceive) when we shoot to evaluate. So that is what we are talking about here.

 

[SMSgt]

All I now is my 12 ga kicks a lot harder with a punkin' ball than with a light skeet load. You can run whatever formulas you want, but that punkin' ball still kicks harder.

 

[WR Moore]

There is a formula for free recoil, I just spent 10 minutes looking for it without success. I'm going to keep looking. Found a formula. This is really intended for long guns and doesn't take reciprocating parts into account.


Free Recoil= M x V squared

V=(projectile weight gr+ [powder weight gr x1.75]) x muzzle velocity f/s divided by gun weight in grains.

Gun weight lbs x 7000= gun weight in grains.

M= gun weight in pounds/64.32

Going through this with a 2.5 lb gun firing a 115 gr bullet, 6.2 gr powder at 1150 f/s we have 2.7 ft lbs of recoil.

A 147 gr bullet, 4.3 gr powder at 920 f/s in the same gun gives 2.56 ft lbs of recoil.

A +P 124 gr loading using 6.4 gr of powder producing 1180 f/s, same gun gives 3.22 ft/lbs.

Going back to Kiwi Cops original question, running the current Hornaday specs for 125 gr & 158 gr .357 loads using 296 powder shows no significant difference in free recoil. Perceived recoil may be an entirely different matter, the formula above doesn't take powder burning rate into account. FWIW, momentum/power factors for the two loads do show a difference : 187.5/125 and 197.5/158, about 5%.

IIRC, the original ammunition requirement for IPSC .357 used the 125 gr load. It had the lower power factor. It was also obviously more effective.

 

[dg101win]

Interesting article in August issue of Shooting Times. Talks about the weight of the powder and its effect on recoil. Talks about 4 values used to calculate recoil force. Bullet weight,bullet speed, weight of firearm and weight of powder.
While it is interesting it is above my pay grade of fully understanding. It mentions the powder(gas) coming out of the barrel,its weight or value assigned to it. Even SAAMI accepts this.

 

[rockquarry]

After all, this is America; if you can't transform something that's very simple into something that's needlessly complicated, it's not worth doing.

 

[Bobbysixkiller]

I know that the 180 grain Remington 44 mag rounds from Wally World sure seem like they recoil pretty hard. Compared to 240 grain anyway. Lots more fire and ear shattering boom too.