This is for physics geeks. lol. I want to understand the effect instability of the shooter has on bullet trajectory. This is not about technique, it's only about the effect of the muzzle not being perfectly still when the bullet leaves the bore. I think it's fun to think about this stuff, but due to my intellectual laziness I usually only take it so far, so then I ask you guys instead of researching the answer, lol. Take the green pill and save yourself the time, or take the red pill and we'll see just where the rabbit hole goes. What you may find is that I took 5 minutes of your time to ask a simple question with an obvious answer.
This is about shooter induced movement of the muzzle, not barrel harmonics, etc. If I mounted a rifle to a moving train to shoot perpendicular to the tracks I think everyone would agree when the bullet emerged from the muzzle it's velocity would include the lateral movement of the train as well. Assuming there was a wall 50 yards from the tracks (and all other variables are inconsequential of course), the point of aim at the instant the bullet left the muzzle would not be the point of impact, but the bullet would impact the wall at some point further down the tracks in the direction the train was heading. Exactly where would depend on the velocity of the train, the muzzle velocity of the bullet, and the distance to the wall, the last two giving the time of flight. Now let's hopefully agree that the same thing would happen if the rifle was on a turntable spinning around, it just might be harder to calculate exactly where it would land. I think this is closer to what happens when a shooter induces instability at the muzzle.
The wobble. Now unless you're the gun shooting Russian robot they just sent to the ISS you probably can't hold a gun 100% perfectly stable, you induce a "wobble". There are well known causes such as breathing, heartbeat, muscle fatigue or just plain nerves, and maybe others. These can vary in amplitude and frequency. Wherever there is movement there is velocity, which is the result of the amplitude and frequency. Consider a wobble caused by breathing could be rather large (in amplitude) but slow in frequency, whereas a muscle fatigue twitching could be high frequency but short (small in amplitude). A wobble is not a like a square wave but more like a sine wave, the muzzle moves so far in one direction but it slows down and then reverses direction, with every movement it comes out of the last one accelerating, reaching peak speed in the middle and then decelerating before reversing direction and doing it again.
My question is concerning the effect this wobble has on accuracy. I want to know if the movement of the muzzle lateral to the bore direction has an appreciable effect on accuracy beyond the simple changing of the point of aim (POA). Consider a bullet leaving the muzzle at the extreme end of a wobble when the muzzle is stationary. Again assuming all other variables are inconsequential, the impact would be at the POA, even though the POA would be off the target by half the total wobble amplitude. I used to think this is all that happened. So what if instead the bullet left the muzzle in the middle of the wobble (crossing the exact center of the target we assume) but therefore at the highest lateral wobble velocity, would it impact even farther off the target?
I've pretty much convinced myself that the wobble will impart lateral velocity to the bullet, but I doubt I'm good enough at math to determine how much. Is it significant or not? I got to thinking about this one day shooting 22s with a stable rest and decent glass I noticed when I would pull a shot they would impact significantly farther out than I pulled off target but along the same vector that I pulled it. I also had an ATN scope that videoed this effect. This was a year or so ago but I did some 22 shooting today and reminded myself I never got to the bottom of it. Please feel free to share your thoughts.
So if it is significant it's no big epiphany or anything, it just helps me understand why some impacts fall far out of my "wobble amplitude" when I still think they are me and not gun or ammo.
This is about shooter induced movement of the muzzle, not barrel harmonics, etc. If I mounted a rifle to a moving train to shoot perpendicular to the tracks I think everyone would agree when the bullet emerged from the muzzle it's velocity would include the lateral movement of the train as well. Assuming there was a wall 50 yards from the tracks (and all other variables are inconsequential of course), the point of aim at the instant the bullet left the muzzle would not be the point of impact, but the bullet would impact the wall at some point further down the tracks in the direction the train was heading. Exactly where would depend on the velocity of the train, the muzzle velocity of the bullet, and the distance to the wall, the last two giving the time of flight. Now let's hopefully agree that the same thing would happen if the rifle was on a turntable spinning around, it just might be harder to calculate exactly where it would land. I think this is closer to what happens when a shooter induces instability at the muzzle.
The wobble. Now unless you're the gun shooting Russian robot they just sent to the ISS you probably can't hold a gun 100% perfectly stable, you induce a "wobble". There are well known causes such as breathing, heartbeat, muscle fatigue or just plain nerves, and maybe others. These can vary in amplitude and frequency. Wherever there is movement there is velocity, which is the result of the amplitude and frequency. Consider a wobble caused by breathing could be rather large (in amplitude) but slow in frequency, whereas a muscle fatigue twitching could be high frequency but short (small in amplitude). A wobble is not a like a square wave but more like a sine wave, the muzzle moves so far in one direction but it slows down and then reverses direction, with every movement it comes out of the last one accelerating, reaching peak speed in the middle and then decelerating before reversing direction and doing it again.
My question is concerning the effect this wobble has on accuracy. I want to know if the movement of the muzzle lateral to the bore direction has an appreciable effect on accuracy beyond the simple changing of the point of aim (POA). Consider a bullet leaving the muzzle at the extreme end of a wobble when the muzzle is stationary. Again assuming all other variables are inconsequential, the impact would be at the POA, even though the POA would be off the target by half the total wobble amplitude. I used to think this is all that happened. So what if instead the bullet left the muzzle in the middle of the wobble (crossing the exact center of the target we assume) but therefore at the highest lateral wobble velocity, would it impact even farther off the target?
I've pretty much convinced myself that the wobble will impart lateral velocity to the bullet, but I doubt I'm good enough at math to determine how much. Is it significant or not? I got to thinking about this one day shooting 22s with a stable rest and decent glass I noticed when I would pull a shot they would impact significantly farther out than I pulled off target but along the same vector that I pulled it. I also had an ATN scope that videoed this effect. This was a year or so ago but I did some 22 shooting today and reminded myself I never got to the bottom of it. Please feel free to share your thoughts.
So if it is significant it's no big epiphany or anything, it just helps me understand why some impacts fall far out of my "wobble amplitude" when I still think they are me and not gun or ammo.
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