Handgun recoil, a question...

OK, I know this may sound like a silly question, so bear with me...

I have always been under the impression that if you take two identical bullet types (such as a JHP), but of two different grain sizes, that the larger bullet will create more recail than the smaller. So, in a .357 (for instance) a 125 grain JHP made by Remington would kick less than a 158 grain JHP made by Remington.

However, I read a post recently that seemed to contradict this. Have I been wrong all-along?

Todd

Only if they are at the same velocity.
Recoil is a momentum (NOT energy) balance. Mass times velocity of the bullet equals mass times velocity of the gun. It takes a little figuring to get it in scientifically consistent units, but the IPSC Power Factor will give you a rough idea. PF = bullet weight in grains times muzzle velocity in feet per second, divide by 1000 to get a manageable three digit number to compare.

Weight of the powder is involved in recoil calculation, too. Bulky powders that have large charge weights recoil significantly more than smaller charges of denser powder. Has to do with the amount of gas jetting out the barrel as I understand it.

What Jim said. Having siad that "felt" recoil may be perceived a little differently than the numbers bear out. In my BHP Practical in .40 as an example the 155 gr. load feels like a lot less recoil than the 180 gr. load. In fact, due to the velocity difference they should be reasonably close, but the 155 gr. load seems to have crossed a lower threshold of recoil for me so feels very light.

MCgunner is correct. The mass of the powder, even though burning and being converted into gas, does add to the forward moving mass, and every formula on recoil takes that into consideration. It is not too significant in many handguns; in a .45 ACP pistol, firing a bullet of 230 grains, the 5-7 grains of the powder charge is not too significant as it is 1/32 of the bullet mass. But in a .30-'06, firing a 150 grain bullet, the 50 grain powder charge is 1/3 the bullet mass, and must be added to the recoil formula.

Jet effect is automatically included as it is part of the movement of the gas and the mass of the gas plus powder is equal to the mass of the unfired powder alone, so the mass is the same whether the powder is powder, or gas, or a combination.

Note I use the word "mass", not weight. "Weight" applies only to objects in a gravitational field; mass applies to objects whereever they are. If a rifle is fired in space, outside the Earth's gravitational field, the bullet will still leave the barrel, and the rifle will still recoil.

In fact, a rifle will recoil even if there is no bullet at all, only a powder charge. The mass of the gasses alone will cause recoil. So it would seem that if we had enough powder to keep up the burning and generation of gas long enough we could keep recoil going and the rifle would keep moving.

If we had liquid "powder" and enough of it, its mass would keep pushing the rifle, and if we pointed the rifle down, it would actually move upward, recoil overcoming gravity. So if we built a big rifle, with big tanks of liquid propellant, and called it a rocket, we might be able to use it to shoot people into space. And we did. Men went to the moon and returned on recoil.

Jim

Recoil is simple physics, Newtons 3rd law, for every action there's an equal and opposite reaction. The principle of conservation of mass, momentum and kinetic energy.

How recoil feels is a subjective matter. Semi auto's feel like they recoil less than fixed breach guns but they are subject to the same laws of physics. What does change with semi's is the time over which the recoil occurs is longer thus if feels like less recoil. Things like grip shape and size, material and relative position to the axis of the bore all change how recoil is felt. Muzzle breaks divert some of the gas in a direction opposite the normal direction of barrel movement. This may actually reduce recoil depending upon the direction of the vented gas but for the most part muzzle breaks reduce the muzzle climb and that makes the recoil appear to be less.

You are not wrong....

Everything the posts told you is also right especially the velocity and power issues BUT...

If you fire a Remington .357 Mag 125 gr UMC JHP round and a Remington .357 Mag 158 gr UMC JHP round out of the same gun, the perception will be the 158 gr round has more of a felt recoil. You will notice the perceived recoil even more in a short barrel gun than the long barrel gun with the heavier bullet too.

I dunno about UMC, but when I tried it a number of years ago, the heavier bullet at the same IPSC Power Factor, fired out of the same gun, had less FELT recoil. I loaded .357s with 200 gr bullets at 875 fps, 158s at 1110, and 125s at 1400 to just make the then Major PF of 175. Everybody who shot them agreed that the 200s had the least unpleasant kick. The 158s were a bit sharper and the 125s were just plain nasty. I ran blind tests; I loaded the gun so the shooter did not know what he was firing. In slow fire the felt recoil was clearly in reverse order of bullet weight. On timed drills, the 200 and 158 grain loads were pretty well equivalent, the small difference in felt recoil did not affect times and hits with the shooter concentrating on the targets instead of the feel of the gun. But the 125 gr load scored lower. Either hits were wilder or times slower... or both.

Why? The estimated recoil on power factor was the same; the computed recoil was within a couple of percent due only to differences in powder charge. Was it the acceleration of the different bullet weights getting up to muzzle velocity? Was it a mental effect of muzzle blast as velocity went from subsonic to transsonic to well supersonic?

Muzzle blast, usually more with a lightweight bullet at a high velocity, usually bothers people more than recoil.

As a practical matter everything that has been said here is generally accurate except that I think there are really several factors involved. One thing that has not been mentioned yet in this post is th mass of the firearm. Now I may be totally all wet here but I feel that perceived recoil is more aligned with the force exerted on you by the fireing of the firearm. In physics:

Force = Mass * Acceleration

Here the mass we are talking about is the mass of things set im motion forward by the explosion. These would be the bullet and powder charge.

Acceleration is the rate of change in veloctity. So the more velocity gained per unit of time the greater the acceleration. The factors affecting this to the positive are the velocity attained by the mass components before they exit the barrel and the time needed for this to be transmitted to you. In a fixed breach firearm this will be instantaneous. In a semi Auto, the acceleration is slowed by the cycling of the action. In addition, the greater the mass of the firearm, the slower the acceleration.

Since recoil is a perceived phenomenon it may actually be a combination of factors and I may be all wet, JMHO

This comment is not a direct reply to the post but to one of the other posts.

The quote of Newton Law is, I believe, incorrect,

The quote should say "equal and opposite action" , an equal and opposite reaction would be the same action as the original.:)

Wow. Lots of good info.

I'll only add that almost any calculation can break down when it comes to subjective recoil. For example, I typically find full house 125 grain .357 loads to be far more offensive than full house 158 grain loads. Same goes for 180 vs 240 grainers in the .44 Magnum. I think it's a combination of blast, flash, noise, and the very "snappy" impulse resulting from firing a light, fast bullet.

Short version: I'm happy with 158 .357 loads all day long, but a box of 125s is enough to really get on my nerves.

Edit: in the rifle, though, it seems very linear to me. Heavier bullets have always equated to more subjective recoil, even as velocities decrease with the heavier bullets. In the .30-06, for instance, the 180/2700 is noticeably more comfortable than the 220/2400. Perhaps the elimination of blast, noise, and "snap" factors allows the true recoil force to make itself felt.

Subjective recoil can differ based upon the height of the bore over the hand, the grip angle, the positioning of the fingers around the grip, the composition of the grip material, and a multitude of other factors.

Basically, less grain-less recoil.
More grain-more recoil.

K.I.S.S.: Keep It Simple Stan.

Hi, DanWesson(?),

No, the quote is correct. There is action and re-action (response to the action); the latter results from the former. Recoil backward is the direct but opposite response to the "ejecta" moving forward. Recoil is absolutely a result of the bullet (and powder/gas) moving forward.

Some writers say that recoil is the result of pressure build up in the chamber; that is true only as the pressure moves the bullet. If the barrel is blocked so that the bullet cannot move, there is no recoil; even though the pressure will build up, it acts equally in all directions so its force cancels out.

Jim

" Why? The estimated recoil on power factor was the same; the computed recoil was within a couple of percent due only to differences in powder charge. Was it the acceleration of the different bullet weights getting up to muzzle velocity? Was it a mental effect of muzzle blast as velocity went from subsonic to transsonic to well supersonic?"

Could it be the "slower" bullet just lengthens the duration of recoil, spreading it out making it "feel" less? Similiar to a gas shotgun?

In the "old shotgun" days, heavier charges of "slower" powder like Green Dot were considered to have less "felt" recoil than the lower charge weight of the "faster' Red Dot.
Of course, the mass of the powder charge compared to the shot charge is very small also. And recoil 'sensations' are felt different when comparing long guns to handguns I would suspect.

Basically, less grain-less recoil.
More grain-more recoil.

That about sums it up..;)

Could it be the "slower" bullet just lengthens the duration of recoil, spreading it out making it "feel" less?
I think this is exactly right, and what I was alluding to with references to "snappy" recoil. Light, fast bullets seem to "hit" my hand faster, even if total recoil is actually less.

I appreciate all of the great input. I have learned more than I ever thought I would...

I realize that the weright of the gun, the type of powder, etc. can make a huge difference, but for clarity's sake... If in the SAME gun and using the SAME powder, just a different grain and type of bullet, I am assuming that a larger grain size equals more felt recoil. Is this correct?

Todd

I think there is still confusion. Both bullet weight and velocity are involved. If you fire a 158 grain bullet at 1000 fps, and a 125 grain bullet at 1000 fps, the heavier bullet will give more recoil. But if the 125 grain bullet has a velocity of 1264 fps, the recoil will be equal. (For this example, I am ignoring the weight of the powder charge.)

Jim