stevecrea's idea
Steve,
You got me thinking. Faster powders equal more recoil, Or, more powder weight equals more recoil? For the sake of argument let's assume a 180 grain 30-06 bullet at 2,600 fps. One load with the fastest powder that will attain that velocity, the other with the slowest.
It would sure take someone with more knowledge of internal ballistics to touch this one; certainly not me. I'd be curious to know if there's an interesting discussion here.
(Also I'm itching to reach post #2000 for another give-away, and this seemed as good a way as any. [:D]
You got me thinking. Faster powders equal more recoil, Or, more powder weight equals more recoil? For the sake of argument let's assume a 180 grain 30-06 bullet at 2,600 fps. One load with the fastest powder that will attain that velocity, the other with the slowest.
It would sure take someone with more knowledge of internal ballistics to touch this one; certainly not me. I'd be curious to know if there's an interesting discussion here.
(Also I'm itching to reach post #2000 for another give-away, and this seemed as good a way as any. [:D]
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Mass velocity of the ejecta (bullet AND powder) determins the lb-ft level of the recoil, assuming the powder gas exits at the same velocity, the heavier charge will recoil more.
A socond consideration is the acceleration rate of that recoil (sharp jab, or slow push), even if the total recoil energy is the same.0 -
This is an interesting question.
I like to separate discussions of recoil into two things.
There is what you might term "physical" recoil, which represents the sum total momentum and kinetic energy of the recoiling firearm, something that could be measured in foot pounds.
There is also what you might term "perceived" recoil, which is the shooters SUBJECTIVE unpleasantness in shooting a gun.
Obviously the second thing is going to be somewhat proportionate to the first thing, but they're not identical. Mass of the shooters torso, gunstock fit, padding, muzzle REPORT, flash, how the gun is held (eg loosely or tightly) and many other factors can affect the physical unpleasantness of firing a gun.
Without much more discussion on this, lets just stipulate that in the real world, very few people are interested in the first thing, and almost everyone is interested in the second thing, ie how much is their shoulder or hand going to hurt when they touch one off!
With respect to the question, if you have two rounds of identical weight leaving the muzzle at identical velocities, the PHYSICAL recoil will be identical. Both rounds will generate the same recoil momentums and kinetic energies.
On the other hand, the round that accelerates fastest, will also accelerate the gun backwards fastest into the shooters shoulder (or hand), and generate the higher perceived recoil.
In practice, the acceleration of the bullet is roughly proportionate to the burn speed of the powder, with faster burning powders generating the propellant gases faster, yielding higher pressures, and higher bullet acceleration.
Obviously all else being equal, more powder = more velocity = more recoil, but that's not what we are comparing here. We're comparing rounds that deliver equal velocity that have different burn rates.
So given the specific issue of burn speed, that speed has very little to do with the total mass of the powder, but much more to do with both its chemical composition, and physical shape.
Some powders just burn faster than others, by design.
With powders of similar chemical composition, all else being equal powder grains with more surface area (eg small flakes) will burn faster than powder grains with less surface area (eg large rods) and generate pressure quicker. Without getting too in over my head here, powder shapes aren't random, they're specifically designed to affect burn speeds and pressure curves.
Another simplified way to look at this is just to consider pressures.
Given two rounds with identical weight bullets that yield identical velocities, the one that generates the higher pressures should accelerate the bullet faster and deliver more recoil.
Hope that made some sort of sense, (and I didn't screw up the physics/internal ballistics too badly!)0 -
It is important to realize that the pressure developed by any load is not constant. And, the point at which the peak pressure is obtained will vary with different loadings. Consider two loads that each reach a peak pressure of 50,000psi. The first load might be with a faster burning powder and reach 50,000psi with the bullet close to the chamber. As the bullet then moves toward the muzzle the pressure drops significantly. The second load with a slower powder reaches 50,000psi with the bullet much nearer the muzzle. When the bullet exits the muzzle, the residual gas pressure will probably be higher for the second load. Since the jet effect of the gas leaving the muzzle is a significant factor in recoil, I would expect the second load to have the higher recoil all else equal. 0 -
My $0.02,
As glabrey has postulated, I believe he may have come to the wrong conclusion.
Now let us all agree this is all in theory so no one's feelings are hurt, there is no "right" or "wrong" we are all guessing at this point.
The factor in calculating energy that is the wild card is called "inertia" & it is the very phenomenon that causes the "velosity squared" factor in the E=MC sq. formula.
In the rifle barrel, if you reach exit velocity in 1/3 & maintain the rest till exit, it will kick like GEEEZ! If exceleration of the bullet is even & uniform for the entire barrel length, there will be noticibly less recoil.
The magic factor is called "inertia". It is the difference between smacking an object or just giving it a gentle shove.
Jim0 -
quote:Originally posted by Tailgunner1954
Mass velocity of the ejecta (bullet AND powder) determins the lb-ft level of the recoil, assuming the powder gas exits at the same velocity, the heavier charge will recoil more.
A socond consideration is the acceleration rate of that recoil (sharp jab, or slow push), even if the total recoil energy is the same.
According to the Taylor recoil calculator that I used to use (can't find it anymore) that is correct. Less powder means less recoil. But Faster powder means more acceleration during recoil. You can overdo it either way. Right before I had my shoulder surgery last December I found I could take 30-06 and .300 mag recoil better than I could take the sharper kick from my 6mm. Even my 6.5 Grendel at the time could hurt with a full load if I didn't have it snugged mostly against my chest and not touching my collar-bone (which is what got worked on).0 -
quote:Originally posted by cussedemgun
My $0.02,
The factor in calculating energy that is the wild card is called "inertia" & it is the very phenomenon that causes the "velosity squared" factor in the E=MC sq. formula.
That is only true as you approach the speed of light. That is what the c is. Classical physics dictate that it is 1/2mv sq.
While the bullet is still in the barrel, it is a closed system and it is when the bullet leaves the barrel, the the energy of the bullet is felt as recoil on the rifle and shooter.0 -
It appears that I did precipitate some interest and discussion.
I do not know about the actual physics or science about burn rates of powders. However, it seems somewhat intuitive that slower burning powders develop their energy over a longer period of time than faster burning powders. We know that the big cases with slow burning powders, such as .264 Winchester Magnum, Weatherby Magnums, etc. need longer barrels to optimize their velocity than smaller, shorter cases, which also use faster-burning powders.
Another clue to what I am getting at is that I have perceived that rifles with big cases, and probably slow-burning powders, emit more of a "boom" for a muzzle blast, rather than the sharp "crack" that you hear from rifles using faster-burning powders.
Regardless, I am interested in what others have to say about this topic.0 -
Remember: when smokeless powders were perfected, the rifle barrels were designed to have the most steel right at the chamber area, and thin barrels.
Now, with modern smokeless powders, all pressure peaks will be mostly in the chamber area. Either fast or slow powders. Exit pressure of the bullet back (part facing the chamber) has many thousands of pounds less lb/in(2) then when it was first pushed out of the casing.
The difference in the location of the bullet (during pressure peak) between fast/slow rates of burn is less than the bullets length! Certainly not beyond the "fat" part of the barrel, no matter what the burn rate.
Conclusion: I have always gone with the exit velocity of the bullet as the cause of the recoil. Not burn rate. Best, Joe0 -
yes, there is no way around physics...mass multiplied by velocity will equal force. So the total recoil will be mass times velocity.
Felt recoil is a different story. you have to add another multiplier/diviser to the equation called time. Of course there is the variable of pressure also. It would be the slope of the tangent of the pressure curve, at any given point in time, that dictates the amount of felt or percieved recoil at that time.
So yes, in theory Stevecrea is correct.
JMHO
Best0
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