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"Pattern" and gun movement


buze
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Ok perhaps this has been asked before, but since there seems to be a reluctance at re-opening old topics, I'm making a fresh one!

 

Anyway, I'm an engineer, and I've started shooting fairly recently, so I keep coming up with the obvious -- but being an engineer, I like to figure stuff out, and not necessarily been fed a textbook about it.

 

My last insight was that one of the reason you 'follow' the target /while/ you shoot is to prevent the gun from stopping -- fair enough, but also that by having the gun moving as you shoot, you will 'spray' the pattern in the direction of the movement by a small fraction, making the pattern more oblong shaped than round, and therefore giving you a /bit/ more chance of splashing that clay.

 

To me, since not all the shots exit the barrels/wad combo at /exactly/ the same time, there is some side momentum involved, and you must have SOME sort of spread along that axis.

 

Think, take a fistful of gravel and toss it slightly sideway. Spreads.

 

My instructors tells me that no, it /doesn't happen/ like that, and the pattern is spread from the gun to the target, but with no axis movement. It's completely counterintuitive to me.

 

Discuss! :-)

 

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Your instructor was correct, someone bothered to work out the maths for it once, you would have to have a gun swing speed of several hundred miles per hour to make a minimal difference.

 

Work out the muzzle velocity of your cartridge and how long the shot column is whilst inside the barrel. From that you can work out how long it takes from when the front of the column leaves the barrel to when the end does.

 

Once you have done the maths and even with the most aggressive swing the barrel will only move an insignificant negligible amount before the entire shot column has left the barrel. Add to that if you are using plastic wads the cup will not have even opened.

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There was a very experienced shot at a clay ground I used to frequent many moons ago who was convinced he could 'string' the shot out horizontally by whipping the muzzles through a target. I was non-committal as I didn't know any different back then, but he grew quite angry when some of the others started ridiculing him for his suggestion.

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There was a very experienced shot at a clay ground I used to frequent many moons ago who was convinced he could 'string' the shot out horizontally by whipping the muzzles through a target. I was non-committal as I didn't know any different back then, but he grew quite angry when some of the others started ridiculing him for his suggestion.

 

I know one or two people who think that today and they're pretty handy too which is the scary thing.

 

In reply to the OP, this has been tested and proved to be a non event, I also recall watching a programme that tested the theory using a pistol and a purpose made jig that whipped the weapon across as it fired, again zero alteration to POI.

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The problem being the distance between the first pellet and last pellet as they leave the barrel is pretty much the same as in the cartridge, so roughly 3 cm, if that. It isn't until the wad leaves the barrel that the pellets separate to any extent. I've attempted a back of the envelope calculation (so it could be way off) for a 1250 fps cartridge with 3 cm depth of shot:

 

1250 fps = 381 m s

 

speed = distance over time so time = distance over speed:

0.03 m ÷ 381 m s = 0.000079 s

 

That means the amount of time you have to influence the pattern (the time between the first and last pellets leaving the barrel) is less than 80 microseconds!

 

The angle formed by a triangle from the gun to a 30" pattern 30 meters away is about 1.4° so to extend the pattern by, say 50%, then you would have to be moving the muzzle of the gun by half that angle over 80 microseconds.

 

I'm no good at angular momentum so I'll cheat and say the distance the muzzle of a 30" barrel will move when a gun is swung 0.7 degrees is 9 mm.

 

Again, speed = distance over time, so the muzzle will have to be travelling at (0.009 m ÷ 0.000079 s = 114 m s) over 250 mph.

 

Having said that, if you are using a plastic wad then I'm pretty sure all of the pellets are cupped until after the pellets leave the barrel so you'll not influence anything. Either way, I need to get out more...

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The shot column, (after it leaves the muzzle) is a bit like a column of soldiers all heading for approximately the same destination, they all eventually arrive at the same place but due to the nature of the formation including any stragglers they arrive at slightly different times and that is the influence of the shot string that increases your chances of hitting the target, ‘all else being equal’!

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The shot column, (after it leaves the muzzle) is a bit like a column of soldiers all heading for approximately the same destination, they all eventually arrive at the same place but due to the nature of the formation including any stragglers they arrive at slightly different times and that is the influence of the shot string that increases your chances of hitting the target, ‘all else being equal’!

That's how I see it. The difference in time between the front and rear shot leaving the barrel will be a lot different to that of front and rear shot reaching the target. Speed of swing may well be multiplied, perhaps.

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What do you mean?

The spread of the shot at 40yrds is about 50-60 times the size of the charge leaving the barrel so, combined with the length of the shot string, the affect of the speed of the swing may be emphasized/accentuated perhaps. The moving plate pattern would be the most telling test.

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