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| one of us |
I see in the recoil formula that the more grains of powder in a reload the more recoil, for ex: a load using 80 grains of Rl22 at 3000fps will have more recoil than a load using 73 grains of I4350 at 3000fps all other components being the same. This is a fictitious example. I was wondering if the burning rate of the powder also plays a role. Does a faster burning powder have a harder/faster recoil than a slower burning powder. My point in this is that if I can have a load at 3000fps that has 5lbs less recoil than another just by choosing a different powder I would like to check it out. Any thoughts? | ||
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Burning rate has no direct effrect on free recoil. The indirect effect is that it would take less powder to reach the same velocity (hypothetically). | |||
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Riciardelli is right. The center of mass of a closed system has to "stay put", unless acted on by an outside force. At the moment the bullet leaves the barrel, the bullet has moved the length of the barrel, and the center of mass of the powder has moved half the length of the barrel. The rifle has to move backward, so that the center of mass of all parts stays in the same place. After the bullet exits, the barrel becomes a rocket, exhausting the gas still in the barrel. | |||
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The recoil formula is an approximation. If there's a big difference in burning rates and charge weights, the slow burning powder will give a little bit greater recoil than the extra charge weight in the formula would indicate, as the higher residual pressure at the muzzle increases the velocity of the exiting gas. The average velocity of the gas as calculated from actual recoil measurements is substantially different for different classes of cartridges, i.e., .30-30, .30-06, and .300 Weatherby Magnum, due to wide differences in muzzle pressure. "Hatcher's Notebook" has a good section on recoil. The bottom line, though, is that if you want to keep recoil down, use the powder that'll get the job done with the lightest charge possible. | |||
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I asked the man who designed the recoil mechanisms of the M107, M110, and M158, "What is impulse in recoil?" He never heard of it. He said, "Just calculate the momentum of the bullet plus the momentum of the powder. I always used 1.5 times the velocity of the bullet for the gas velocity."  | |||
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The peak force of recoil, which some argue can be felt, is basically the product of the peak chamber pressure and the area of the bullet. Faster burning powders will reach the peak pressure faster and drop off faster. Slower powders will reach it more slowly and sustain it longer. But given equal maximum pressures, the peak rearward thrust is identical. | |||
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quote:Clark is right as far as the calculations go. Impulse is force x time; momentum is mass x velocity. If you write down the units of each, you will see that they have the same units. Impulse is the force on your shoulder over time that it takes to hold the rifle while it creates the momentum for the bullet and gasses. | |||
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Actually there is such a thing as "Impulse Rate". The rate of change( dM/dT) of momentum is called Jerk. Good Luck! | |||
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And that rate of change in momentum, since the mass of the gun doesn't change during firing, represents the instantaneous pressure x the bore area. Nothing else. So the "jerk" depends on the peak pressure you're loading to, not the burn rate of the powder. | |||
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| one of us |
Try shooting a 500 N.E. with 4831, then switch to 4350, then tell me the slower powder kicks the same...There is a real difference, the 4350 kicks much less... | |||
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Most recoil calculators assume a velocity for the exit gasses at the muzzle, generally in the vicinity of 4700 fps. Of course, some powders will result in more or less gas velocity in application, and this difference from the assumed velocity is exacerbated by the fact that it is squared in the formula. Ray is right, 4350 has a larger pressure drop than 4831 in a 500 NE, and will have less recoil where both bullets exit at the same velocity. | |||
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1) The recoiling rifle's rearward velocity would be at any time proportional to the area under the curve of pressure [minus bullet friction correction] times time. 2) The recoiling rifle's rearward acceleration at any time would be proportional to the pressure [minus bullet friction correction] at any time. 3) The jerk would be proportional to slope of pressure vs time. A faster powder could produce more jerk, but I think the velocity and acceleration are what is felt. -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. | |||
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| one of us |
No, if you're defining the "jerk" as the change in momentum over time, the slope of the pressure/time curve has nothing to do with it. Only the pressure at that instant. I think this is a moot point anyway. I don't believe the folks who say they can feel the difference in guns' acceleration rates. I think it comes down solely to impulse, all of which is developed in about 1.5 milliseconds at the most if you include the "blowdown" time for depressurization of the bore and chamber. I don't believe your nervous system or mine can distinguish events occurring within such a short interval. Just the integrated area under the force/time curve, which is the total momentum. | |||
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When I went to college there was: 1) position 2) change in position with respect to time = acceleration This was the derivative. 3) change in change in position with respect to time = acceleration This was the second derivative. 4) change in change in change in position with respect to time = jerk This was the third derivative. If the acceleration on the rifle is proportional to the pressure, then the recoil velocity of the rife is the integral of the pressure and the recoil jerk is the first derivative of pressure. -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. | |||
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i would think that a faster powder would produce a "faster" recoil. or more of a "kick" during shooting. and a slower powder would be more of a "push" ie the diffrence between someone punching your shoulder or just shoving it.... they still use X lbs of force but its just delivered diffrently. like I shot a 30-06 (rem 700) and that hurt due to the kick of the rifle. then I shot a .50bmg (barret) and it was more recoil but it did not feel as bad due to the "speed" of the recoil | |||
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quote:#2 should reference velocity...not acceleration | |||
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quote:To be a good test of this you would need to experiment with the same rifle. You would have to develop two loads that shot the same velocity...one with a slow powder for caliber and one with a fast powder for caliber. I think that it would be very difficult to tell a difference in pure recoil. Don't forget that muzzle blast will be different and that makes a difference in recoil perception eventhough it doesn't have anything to do with the amount of "push" on your shoulder. | |||
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when i get a rifle I will. I will be going to the only 100 yard range in the area next sunday. its a private club and they constructed a 100yd "tunnel" to shoot in... as its the only way to get a rifle range here in the middle of suburbia. (NJ SUCKS!) next "orientation" is in january and I should be able to afford a decent target rifle by then. [ 11-03-2003, 19:41: Message edited by: Unstable ] | |||
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I don't think anyone will be able to quantify the difference in recoil from fast to slow powders based on the momentum of the bullet. Interestingly enough, the shotgun guys SWEAR just like Ray does, except they say that slower powders create "less" recoil. Recoil is caused by both momentum (the energy of the bullet and mass of the powder moving out), plus the jet effect of the remaining powder leaving the barrel. "Assuming" the powder leaves the barrel at the 1.5 times the speed of the bullet is a BIG assumption. I would suspect it does not hold at pistol velocities, etc. If there IS a difference between 4350 and 4831 in the 500 NE, the difference has to be in the jet effect, as there is not enough difference in ejecta weight to notice. Muzzle pressure with the 4831 would be higher. Someone with Quickload should be able to run the exact numbers. FWIW, Dutch. | |||
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quote:I'm sorry, Clark, but IMO that's total gibberish. I don't believe there's any sensation of recoil that could be related to what you're calling "jerk," which is the variation of acceleration with time. | |||
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NotRicochet, I don't believe that the change in rifle accleration from recoil with respect to change in time has an associated sensation either. Irv went afield from my recollection of how the word jerk is used and you went further, so I recited what I learned in college about the meaning of the word "jerk". I don't define "jerk" as change in momentum with change in time. I define it as change in acceleration with change in time. Maybe that's just because that is the only way it was ever explained to me in college. I don't claim to be an expert in the verbiage. The man who designed the M158 recoil system says there was, "480,000 pounds of reaction". He has been showing me how to absorb that with a constant force independent of the magnitude of the force. I am trying to make a pistol based on this, and when I talk to the man, there is always some lingo that is new to me. -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. [ 11-04-2003, 08:17: Message edited by: Clark ] | |||
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OK. Just so we all are talking about the same thing. I really didn't mean to be offensive, but we didn't have a defined term called "jerk" in my college physics courses. | |||
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1. Position. 2. dp/dt change in position /change in time = velocity. 3. dv/dt change in velocity / change in time = acceleration. 4. da/dt change in acceleration / change in time = jerk Physics 111 | |||
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| <bigcountry> |
As a old physics type myself, I understand what you guys are saying. And agree that there is a different rocket effect going on with different powders. To break it down, think of a drag race with two cars. One car's acceleration is very linear, and constant. The other guys car doesn't do well accelerating at low speeds, but over 200mph, acceleration triples the first car. And the first car wins. His velocity accross the finish line is slower but da/dt was very smooth. Now, even though I believe the affect is there, all these things are so miniscule, that we wouldn't realize them and in the end, its initial Vo of that bullet coming out of the barrel. | ||
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Powder has a large effect on recoil, no powder, no recoil. | |||
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No primer, no recoil, either. | |||
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I think the question is, "What is the effect of [powder mass] times [ejected powder mass velocity] on the formula for rifle recoil?" 30 years ago I was confronted with a problem in Differential Equations class: Find solutions for: y''(x) - y(x) = 0 I wrote: y = 0 [a point for a laugh?] I received one point. If I had my life to live over, I would do my homework. -- A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian. | |||
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