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Thread: Velocity vs Barrell Jump?

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    Member Smokey's Avatar
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    Default Velocity vs Barrell Jump?

    Saw a hunt show on TV a cpl nights ago and got me scratch-in my noggin a bit...?
    Host said to hold down or apply some downward pressure on a shotgun slug barrel because gun would jump before bullet exited the barrel distorting accuracy. Hmmm, the newer sabot slugs are trucking along near 1900fps for the most part - 30-30 or 4570 range. I am not sure I buy his statement.
    Anybody have some thoughts?
    If a gun can / does jump before the bullet exits what velocity range would you expect that to break at????
    This should be fun!

    Murph - whats ya say Ole wise one?
    When asked what state I live in I say "The State of Confusion", better known as IL....

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    you might be able to hold the barrel down when shooting off a bench, but how ya gonna hold it down when hunting? Seems like even if it did jump before it came out, you'd want to sight it in for that "jump" cause other wise it'll fling your bullet over the back of that buck. I have my doubts it would make it just enough to matter.
    Eccleasties 8:11 Because the sentence against an evil deed is not executed quickly, There for the hearts of the sons of men among them are given fully to do evil.

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    Moderator stid2677's Avatar
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    Come on Smokey,, ya know you can't believe everything you see on TV.. LOL
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    "....show on TV"...."Host said...."

    'nuf said.
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    Plenty of videos on youtube, I can see no muzzle jump until the bullet exits.

    Check out how the barrel flexes like a noodle.

    http://www.youtube.com/watch?v=AqgPu...eature=related

    Watch the scope in this video

    http://www.youtube.com/watch?v=s5pVya7eask
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    Quote Originally Posted by stid2677 View Post
    Come on Smokey,, ya know you can't believe everything you see on TV.. LOL
    Hey Steve, yes you are correct - why just a few years ago a chap on tv promised great change - many believed!

    On a serious note, I have tightened groups on many bigger caliber guns by adding a firm grip to the sling or adding downward pressure to a barrel - so there is some merit - all actions have an equal reaction.
    When asked what state I live in I say "The State of Confusion", better known as IL....

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Smokey View Post
    Hey Steve, yes you are correct - why just a few years ago a chap on tv promised great change - many believed!
    You're talking about that nut job from Florida who predicted the rapture last year, right?
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
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    Quote Originally Posted by stid2677 View Post
    Plenty of videos on youtube, I can see no muzzle jump until the bullet exits.

    Check out how the barrel flexes like a noodle.

    http://www.youtube.com/watch?v=AqgPu...eature=related

    Watch the scope in this video

    http://www.youtube.com/watch?v=s5pVya7eask
    Kinda reminds me of my honey-moon!
    When asked what state I live in I say "The State of Confusion", better known as IL....

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    Quote Originally Posted by stid2677 View Post
    Come on Smokey,, ya know you can't believe everything you see on TV.. LOL
    You mean you can't? Aw, I'm sooooo confused now. LOL

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    Quote Originally Posted by stid2677 View Post
    Come on Smokey,, ya know you can't believe everything you see on TV.. LOL
    But they said on that one commercial that if I drank that type of powder in my milk I would get a bunch of muscle and kill a B&C buck every year!!!!
    Eccleasties 8:11 Because the sentence against an evil deed is not executed quickly, There for the hearts of the sons of men among them are given fully to do evil.

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    They also say that if you use this cream it will grow more hair and if you use that cream it will make things bigger. My question is how does one apply said creams?? Would it not give you a big hairy hand??

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    On a semi auto yes and the movement is from the bolt moving.It should not be noticed in any way by the shooter and probably a fancy machine
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    Default Recoil

    Recoil comes from 2 sources - the reaction from accelerating the bullet to velocity and the gas effect from the muzzle blast.

    The gun starts to recoil before the bullet leaves the barrel - all the force of recoil from accelerating the bullet comes before the bullet leaves the muzzle. We see the effect of the recoil rise in shooting heavier bullets in lighter guns esp. handguns. Heavier bullets will shoot higher than lighter bullets at close range in handguns because the recoil is heavier and the slower heavier bullet is in the gun longer during the recoil cycle. The same effect happens in rifles but the results depends on the weight of the rifle, bullet weights etc. and may not be as noticeable.

    The recoil from the gas obviously doesn't occure until after the bullet has exited the muzzle.
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    Quote Originally Posted by stid2677 View Post
    ....Would it not give you a big hairy hand??

    Steve
    Naw, that's something different. I hear tell it'll make you go blind too.
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
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    Quote Originally Posted by iofthetaiga View Post
    Naw, that's something different. I hear tell it'll make you go blind too.

    You know its true
    Eccleasties 8:11 Because the sentence against an evil deed is not executed quickly, There for the hearts of the sons of men among them are given fully to do evil.

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    Quote Originally Posted by Smokey View Post
    On a serious note, I have tightened groups on many bigger caliber guns by adding a firm grip to the sling or adding downward pressure to a barrel - so there is some merit - all actions have an equal reaction.
    I belive holding the sling tighter just holds the rifle still. Competition shooters wrap themselfs into there slings to hold the rifle tight and little to no movement.

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    Quote Originally Posted by Smokey View Post
    Saw a hunt show on TV a cpl nights ago and got me scratch-in my noggin a bit...?
    Host said to hold down or apply some downward pressure on a shotgun slug barrel because gun would jump before bullet exited the barrel distorting accuracy. Hmmm, the newer sabot slugs are trucking along near 1900fps for the most part - 30-30 or 4570 range. I am not sure I buy his statement.
    Anybody have some thoughts?
    If a gun can / does jump before the bullet exits what velocity range would you expect that to break at????
    This should be fun!

    Murph - whats ya say Ole wise one?
    It is easy to work out. Google physics equation acceleration and work out the acceleration and time. You can find out the time the projectile is in the barrel and its acceleration. Once this is done, you can move on to determining the displacement of the firearm in which the projectile was. You'll find out it is very, very little since the projectile has to overcome the intertia of the firearm and your body.
    Regarding the statement that heavy bullets print higher, this is because the bullets fly with a higher arc at their lower velocities, lower mass projectiles fly faster and have flatter trajectories.
    You can see some movement when loking at slow-motion flicks of heavy guns fring, like a 155mm cannon. But the projectile mass compared to the barrel mass is much higher than that of what we are shooting.
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    Quote Originally Posted by alaskabliss View Post
    I belive holding the sling tighter just holds the rifle still. Competition shooters wrap themselfs into there slings to hold the rifle tight and little to no movement.
    Fun thread so far fellas, some good info and some good laughs!
    alaskabliss, I should have been a bit more specific. When shooting off of sandbags I have used my free hand to grip the sling near the foreand and applied a firm hold which many times has tightened my groups - I know what you mean on competition shooters using no rest though and wrtapping up in sling.
    I agree Nitroman - arc from big ole slow bullets is much greater creating higher prints.... Good input!
    I am thinking if hits are improved by holding gun tight it is likely more attributed to a better rest ( everything is tight and more consistant) than taming a whipping barrel....
    When asked what state I live in I say "The State of Confusion", better known as IL....

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    In the case of the bullets printing higher I'm refering to the same sight settings - not with different bullets sighted in at a given range where the arc of the trajectory does come into play.

    An extreme case I ran into was shooting cast bullets in a lightweight .378 Weatherby Magnum. I bore sighted the gun with the cast bullets and the cast bullets were pretty much dead-on at 50 yds or less. When firing heavy jacketed bullets the gun shot about a foot high at 50 yds. with the same sight settings. There is some difference in the trajectory but not enough to explain that difference - neither bullet has had enought time to drop.

    In large caliber pistols the effect of shooting heavy bullets is well known. For example, with my .500 S&W the 440 gr. bullets impact a much higher than the 325 gr bullets at 25 rds. I don't know where the paths cross - I'd guess 50 -75 yds.

    The lighter the gun and the heavier the bullets the more you will see the effect.

    The difficulty in working things out with physics is that the gun is against your shoulder and you add to the mass. You also have the offset of the stock drop which causes the gun to rise in recoil - the gun is not only coming back in recoil but also starting to rotate.

    For a gun suspended as a pendelum it becomes a classic physics problem.


    Quote Originally Posted by Nitroman View Post
    It is easy to work out. Google physics equation acceleration and work out the acceleration and time. You can find out the time the projectile is in the barrel and its acceleration. Once this is done, you can move on to determining the displacement of the firearm in which the projectile was. You'll find out it is very, very little since the projectile has to overcome the intertia of the firearm and your body.
    Regarding the statement that heavy bullets print higher, this is because the bullets fly with a higher arc at their lower velocities, lower mass projectiles fly faster and have flatter trajectories.
    You can see some movement when loking at slow-motion flicks of heavy guns fring, like a 155mm cannon. But the projectile mass compared to the barrel mass is much higher than that of what we are shooting.
    Living the urban lifestyle so I can pay my way and for my family's needs, and support my country. And you?
    ".. ask not what your country can do for you, ask what you can do for your country" JFK

  20. #20

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    I gots me a Ithaca 37 Featherlight 12 ga. slug gun that knocks the snot out of me every time I let one fly. It shoots better groups if I shoot it just like a 22 and don't put the death grip on it. This is one of the best shooting slug guns I've ever owned but I hate it so bad that it never gets used unless some idjut wants to borry it. They never ask again.

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