Please explain bullet weights.

[OH25shooter]

Examples: 9mm 115 grain vs. 147 grain. Or a 44 magnum 180 grain round compared to a 240 grain? I know a heavier grain bullet will drop slightly more, but can it be felt in recoil? The confusion comes from looking at 44 special. Some are 180 grain and others are 200 or 240 grain. Does the 180 kick less than the 240? I hope that's not too confusing.

 

[Glock19Fan]

It depends.

Generally, the heavier bullets dont contain as much powder, either becuase there isnt much room (becuase heavier bullets are generally longer, and protrude into the case more), or becuase the pressure would be too high with a heavier bullet. This kind of evens out the recoil.

I find that heavier bullets have slightly more recoil, but less muzzle flip. Lighter bullets have a little less recoil, but more muzzle flip.

Personally, I shoot the heavier bullets better.

 

[J.M.]

OH25SHOOTER - Unless you are compairing normal loads to target loads - rule of thumb states says heavier bullet will hit the target higher and have more (but not always less agreeable) recoil. - JM.

 

[ExMachina]

Others here can give you a more complete answer, but your question seems to really be two: 1) what factors determine felt recoil and 2) why load different bullet weights

As to recoil, the formula for recoil energy would be the same as that for bullet energy, where the energy increases proportionally to the weight of the bullet, and to the square of the velocity. So, a 45ACP firing a 200gr bullet at 975fps (421 ft lbs muzzle energy) will produce less felt recoil than if the same gun were firing a 165gr bullet at 1250fps (573 ft lbs me). So, the easiest way to ramp up muzzle energy is to increase the bullet's velocity, which can be accomplished by increasing chamber pressure and/or decreasing bullet weight. Therefore, if a specific cartridge is always loaded to maximum pressure (taylored to a specific firearm), lighter bullets will end up yielding the greatest muzzle energy AND the greatest felt recoil.

The advantage to heavier bullets is that they retain their energy better, both over distance and while penetrating objects. Over long ranges, heaver bullets are also less susceptible to wind drift, and so are more accurate. However, becasue heaver bullets travel slower on average, they will exhibit greater bullet drop.

 

[J.M.]

OH25shooter - Like I said before, if you are compairing like loads, heavier bullets will tend to recoil more.

Lets look at the two bullet weights that you asked about, both loads will be loaded to 14,000 CUP's just to keep this an apples to apples compairson, and both assume a 3lb gun.

Standard load disclaimer applies:

180gr jacketed - 14,000 CUP - 7.8gr of Accurate #5 - 1000 fps = 4.71 ft/lbs of free recoil energy.
240gr jacketed - 14,000 CUP - 9.0gr of Accurate #9 - 811 fps = 5.62 ft/lbs of free recoil energy.

All these numbers are just that...numbers, you might find that muzzle blast is a bigger factor in your precieved recoil that free recoil energy is...I usually find that heavier bullets have more recoil, but it is less objectionable to me that the sharp recoil of a light /fast round. You'll need to buy a box of each and give it a try to see what works for you. - JM.

 

[ExMachina]

180gr jacketed - 14,000 CUP - 7.8gr of Accurate #5 - 1000 fps = 4.71 ft/lbs of free recoil energy.
240gr jacketed - 14,000 CUP - 9.0gr of Accurate #9 - 811 fps = 5.62 ft/lbs of free recoil energy.

This example is perfectly valid but so is this one (which shows the opposite trend):
-------------------------------
45ACP (taken from Lee Data Manual)
185 gr--17,000 CUP--8.2gr--1044 fps = 5.39 ft-lbs recoil
185 gr--17,000 CUP--7.2gr-- 993 fps = 4.77 ft-lbs recoil

230 gr--17,000 CUP--4.0gr-- 732 fps = 3.59 ft-lbs recoil
--------------------------------

So I was too hasty in simply stating that recoil was directly scaleable to the muzzle energy. It's not. Rather it must be considered as an addition to the bullet's energy.

"Felt-recoil energy" is a measurement expressing the kenetic energy of the gun in recoil, taking into account the weight of the gun and the added impulse of excess powder gasses which do not otherwise affect the bullet or chamber pressure (the rocket effect). Consequently, inefficient loasd can actually increase the "recoil energy" of a gun w/o increasing the energy of the bullet by wasting powder gasses.

Sorry if I caused any confusion w/ my earlier post.

 

[unspellable]

Recoil

The chracteristic of a given load that relates to recoil is NOT energy, but rather, impulse. The impulse is equal to the mass of the bullet times its muzzle velocity plus the mass of the powder times its average muzzle velocity. Note that in calculating impulse, the velocity is NOT squared. It's tricky to measure the average velocity of the powder gas so various rules of thumb are used. For handguns, one rule of thumb is the average powder gas velocity will be 1.5 times the bullet velocity.

Given the impulse of the catridge, divide it by the mass of the gun and you have the recoil velocity. Half the mass of the gun times the gun's velocity squared gives the recoil energy.

For full house loads this generally works out to more recoil with a heavier bullet. There will be more jump (Jump is that part of the recoil motion which occurs between ignition and the bullet exiting the muzzle.) with a heavier bullet so from a handgun it will strike higher at short ranges.

 

[ExMachina]

The chracteristic of a given load that relates to recoil is NOT energy, but rather, impulse.

Both impulse and energy are equally valid (or invalid) measures of percieved recoil!

The recoil impulse (I = [weight of gun]/32.2*[velocity of gun]) is simply the momentum of the gun and corresponds to the more subjective quality of "sharpness" in recoil. The recoil energy (Recoil Energy = 0.5*[weight of gun/32.2]*[velocity of gun]^2 ) is a better measure of how much energy YOU will have to expend to counter the recoil--this corresponds to how "punishing" a gun/load migh be.

Note here again, that my first post was wrong. I was talking out of my as* w/o stopping to think about the (very important) factor of gun velocity :banghead:

 

[unspellable]

Recoil

I was talking about determining the objective recoil produced by a given cartridge load and gun combination.

Once calculated, you have numbers for both the momentum of the gun and its kinetic energy.

Perceived or subjective recoil is another ball of wax that drags ergonmics, physiology, mental state, muzzle blast, etc. into the discussion.

Ergonmics involves the shape of the gun and grip, what combination of straight line recoil and muzzle flip is involved etc.

Physiology involves how tender your paw and your nerves are, whether the momentum or the kinetic energy of the recoiling gun is more significant, etc.

You get the idea.

 

[Mikul]

In order to get a bullet moving, you have to overcome the inertia of the bullet. Heavier bullets have more inertia to overcome which give them more recoil for a cartridge producing the same pressure with a lighter bullet.

 

[Norm Lee]

bullets, recoil, physics and such

Let's consider the physics for a second. The bullet and the gun are not going to have the same energy. The bullet's energy will always be greater. To calculate recoil energy we need to know the velocity of the gun to do the half M V squared thing. I assume we already know the mass. We know from Newton's third law that bullet and gun momentum will be equal so we can calculate gun velocity if we know bullet mass and velocity. MbVb=MgVg.

Then we can get recoil energy.

Now suppose we shoot a bullet of 200 grains weight at 500 fps and a bullet of 100 grains weight at 1000 fps. The lighter bullet has 2 times the energy. Recoil energy is the same in both cases.

Recoil energy is proportional to bullet momentum, not energy.

I've conveniently ignored contribution of powder, you'll have noticed. But that's for another discussion.

Cheers,

Norm

 

[OH25shooter]

Thanks everyone. Seems a little like trying to figure out what E=mc2 means. However, it appears from the answers a great deal of thought was used and I appreciate the explanations.

 

[Sunray]

That Newton fellow said it best. Even made it a law. Every action has an equal and opposite reaction. When a bullet starts moving, it exerts the same pressure backwards as is applied to it. There is a host of factors that absorbs some of this pressure. What remains is the felt recoil.
"...the inertia of the bullet..." Stationary objects have no inertia. They have potential energy. Issac covered that one too. Objects in motion stay in motion until acted upon. So too with stationary objects. Cause a solid to change to a gas, quickly and the stationary bullet isn't any longer. Only when a bullet is in motion does it have inertia.