I am confused. The loading books generally list muzzle energy in ft/lbs. A lighter and faster bullet in any particular cartridge is reported as having more muzzle energy than a heavier bullet. Yet we all know that a cartridge loaded with a heavier bullet produces more recoil than a lighter bullet in the same cartridge. How?

calculations of energy are not the same as for recoil

Energy is calculated on the SQUARE of the velocity.

It's why a little velocity increase can yield a lot of increase in energy.

Interesting. I can’t find where muzzle energy for a lighter bullet in the same cartridge is greater than the next heavier bullet. The velocity is greater but not energy.

I do see some varying muzzle energies listed in the Sierra manual but those are more specific to a given powder than the overall loading data.

You are right about recoil, heavy equals more. The recoil shown is based on a 8-pound rifle and listed charge weights from the Sierra manual.

Gentlemen, thanks for your input and information. A case in point, using max loads for the 30-06 from my old Hornady handbook. A 130 grain bullet at 3300 fps produces 3144 ft/lb energy, whereas a 190 grain at 2700 fps produces less; 3076 ft/lb. With the understanding that every force requires an equil and opposite force, these numbers would suggest that the recoil of the two loads, in ft/lb, fired out of the same rifle, should be about the same. As we know, they are not.

I am aware of the formula that is used to determine muzzle energy based upon the weight and velocity of the bullet, which raises an interesting point. Velocity includes a time factor. So, I suppose, with the formula, the resultant 'ft/lbs' do as well. We have exceeded my very long ago high school physics class!

That's ft-lbs, Force x Distance, and is defined as Work. There is no Time factor.

Energy is dependent on Mass and velocity at any point in the bullet's path, where mass is dependent on the Weight of the bullet divided by the acceleration of gravity, M = W/g.

Energy = 1/2 x W/g x V squared

I'm really going out on a limb here, but if a light, faster bullet and a slower, heavier bullet produce more or less same muzzle energy, could it be that the recoil from the heavier bullet is greater just because it spends more time in the barrel? That wild assumption would actually correlate rather well with the recoil numbers for the 30-06 listed above.

This is what I think.

The powder charge makes a difference. Ignition doesn't make it weigh any less, so the weight of the powder charge also contributes to the recoil as the gases exit the muzzle. Redirecting some of these gases is how a muzzle brake works.

A heavier bullet tends to cause a higher average pressure (not necessarily a higher peak just a higher average). A higher average pressure would result in the gases leaving the muzzle at a higher velocity. That means the charge would also leave at a higher energy.

quote:

Originally posted by gwahir:
...if a light, faster bullet and a slower, heavier bullet produce more or less same muzzle energy, could it be that the recoil from the heavier bullet is greater just because it spends more time in the barrel? ...

Hey gwahir, Actually it is because the Total Ejecta(Bullet + Powder) is larger with a Heavy Bullet.

There is also "Perceived Recoil" which can play mind games on a person. The shape of the stock, recoil pad, scope positioning which results in some unique face placements on the stock, total firearm weight, report volume, shooting position, etc., can all conspire to give an impression that the amount of Recoil is not really what it indicates. Generally a HEAVY Recoil rifle that fits me well appears to have less recoil than one that does not fit me, even if it is the same weight and barrel length. Toss in a Decellerator and my mind says for sure it is less recoil, though it will actually be the same.
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The "higher average pressure" that TheBig Guy mentioned really depends on the powder being used. Some will do as he mentioned and some won't. Also, some Cartridges just fit in specific Powder Burn Rates where they can maintain a higher average pressure better than other Cartridges. You can easily see it by studying the Load Manuals.

Good Hunting and clean 1-shot Kills.

quote:

if a light, faster bullet and a slower, heavier bullet produce more or less same muzzle energy, could it be that the recoil from the heavier bullet is greater just because it spends more time in the barrel?

I have no answer to your question but I found it interesting so I ran some numbers through QL. I used a 190 and 125 grain bullet for comparison. I ran them at 3140 +- ft-lb of muzzle energy. The 125 had a barrel time of 1.09 ms and the 190 had a time of 1.3 ms. The 125 had recoil of 19.29 ft-lb and 22.08 ft-lb for the 190. There is a difference but not a lot. I didn’t spend much time going over the data. The weight of the powder charge is calculated into the Recoil equation so the 125 gains a little there.

Rifle Recoil

By Chuck Hawks

Recoil is generally expressed as "free recoil" and measured in foot-pounds of energy. Free recoil means that the rifle is allowed to move backward unrestrained after being fired. It something (like your shoulder) restrains the rifle's rearward motion, then your shoulder must absorb the energy generated by the recoiling rifle. Bummer!

Recoil is measured in something called a recoil pendulum, or calculated by mathematical formula based on Newton's physical law that says for every action there is an equal and opposite reaction. MV = MV (mass times velocity equals mass times velocity), the momentum must be equal on both sides of the equation. Newton's law explains why rocket motors are able to propel the space shuttle into orbit, and why guns kick.

The principle factors that must be considered to calculate recoil are bullet weight (mass), bullet velocity, powder charge, and rifle weight (mass). The mass times the velocity of everything ejected from the muzzle of a rifle (principally the bullet and power gasses) will be equaled by the mass times the velocity of the recoiling rifle.

The majority of authorities seem to agree that recoil of over 20 ft. lbs. will cause the average shooter to develop a flinch, which is ruinous to accuracy. I estimate that about 15 ft. lbs. of recoil energy represents upper limit of the average shooter's comfort level. Above that recoil becomes increasingly intrusive. The effects of recoil are cumulative. The longer you shoot, and the harder a rifle kicks, the more unpleasant shooting becomes and the more likely you are to jerk the trigger or flinch.

The free recoil velocity is how fast the gun comes back at the shooter. The faster a gun comes back at you the more it hurts. This is because your body has less time to give with the recoil. You have probably heard about the "long, slow push" touted by some big bore fans as opposed to the "sharp rap" supposedly delivered by high velocity cartridges. Recoil velocity is a real, measurable effect. But the "long slow push" appears to be a myth. Both my own personal experiences with a reasonable range of rifle calibers from .22 LR to .458 Win. Mag. and a quick perusal of the "Rifle Recoil Table" will show that the recoil velocity tends to increase as the recoil energy increases. The following examples of recoil energy and velocity are all measured in 8 pound rifles. (Caliber [bullet weight, muzzle velocity] = free recoil energy & free recoil velocity.)

* 6mm Rem. (100 grain, MV 3100 fps) = 10.0 ft. lbs. & 9.0 fps
* .270 Win. (140 grain, MV 3000 fps) = 17.1 ft. lbs. & 11.7 fps
* .30-06 (180 grain, MV 2700 fps) = 20.3 ft. lbs. & 12.8 fps
* .35 Whelen (250 grain, MV 2400 fps) = 26.1 ft. lbs. & 14.5 fps
* .450 Marlin (350 grain, MV 2100 fps) = 35.7 ft. lbs. & 17.0 fps
* .458 Win. Mag. (500 grain, MV 2050 fps) = 68.9 ft. lbs. & 23.5 fps

In the typical examples above, as the bullet weight goes up the muzzle velocity (MV) goes down; but the recoil energy and recoil velocity both continue to go up. The heavy bullets at relatively low velocity do not deliver a "long slow push," they deliver a progressively harder and faster blow to the shooter. Note that the high velocity .270 with its 140 grain bullet has a recoil velocity of only 11.7 fps, while the relatively low velocity .450 Marlin with its 350 grain bullet at 2100 fps has a recoil velocity of 17 fps!

Rifle weight plays an important role in determining the amount of recoil delivered to the shooter's shoulder. For any given caliber and load, a lighter rifle kicks more than a heavier rifle. Which is why I avoid ultra-light hunting rifles. Here are a couple of examples showing the effect rifle weight has on recoil energy and velocity when shooting the exact same load.

* .300 WSM (180 grain, MV 2950 fps), 6.5 lb. rifle = 30.8 ft. lbs. / 17.5 fps
* .300 WSM (180 grain, MV 2950 fps), 8.5 lb. rifle = 23.6 ft. lbs. / 13.4 fps

* .45-70 (300 grain, MV 1900 fps), 7.0 lb. rifle = 26.6 ft. lbs. / 15.6 fps
* .45-70 (300 grain, MV 1900 fps), 8.5 lb. rifle = 21.9 ft. lbs. / 12.9 fps


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Have returned from visiting grandchildren. Mickin, your numbers look quite close. With the muzzle energy more or less the same, barrel time is a real variable between the two bullets. I know the speed of the 57 chevy increased in relationship to how long the gas pedal was pushed! Rifle recoil speed would increase according to the amount of time the rifle is subjected to the muzzle energy, or, at least, all the factors that produce muzzle energy.

Recoil (and bullet penetration) depend on
Momentum. Momentum is Mass x Velocity.
Recoil as stated earlier is dependant on
everything going forward.
Energy will determine wound dimensions (maybe).
As Elmer Keith stated killing power depends
on the size and depth of the hole.
Good luck!