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  1. #21
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    Wink Re: Why would one file the tip of a bullet?

    Mabey his rounds OAL was too long to fit in his box magazine

  2. #22
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    Default Re: Why would one file the tip of a bullet?

    Quote Originally Posted by Hawk View Post
    Well, there is a process used by precision rifle shooters to "true" the tip of their bullets so that they are all exactly the same. Has to do with making sure the ballistic coefficient of the heads are equalized.

    This could be what they are trying to depict in the film.

    Info on the Ballistic Meplat Uniformer: http://www.jarheadtop.com/BMU_Details.htm



    You forget that movies are geared towards "making sense" to the general audience of those movies.


    Jan
    So long and thanks for all the fish.

  3. #23
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    Default Re: Why would one file the tip of a bullet?

    in the film he files them down, creates a cavity, and then fills it with mercury

    I don't remember why, it was hard enough just staying awake watching the movie.

  4. #24
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    Default Re: Why would one file the tip of a bullet?

    Quote Originally Posted by IronSight View Post
    in the film he files them down, creates a cavity, and then fills it with mercury
    I admit not having seen the movie, and from what has been said so far, I probably won't.

    But what in the world would mercury be good for here anyway? This sounds like a really dumb attempt at copying Hardy Krüger using his cyanide tipped cross bow darts in "The Wild Geese".


    Jan
    So long and thanks for all the fish.

  5. #25
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    Post Re: Why would one file the tip of a bullet?

    I would like to start off by saying this is my first post as I am a new member of this forum. I have been reading for a few weeks and decided to finally post. As background I work for the US Army as an aero-ballistic research engineer with concentration mainly in small caliber munitions (up to 40mm).

    That being said there are a few reasons why one may file the tip of a bullet many have been mentioned above but offer little explanation so I will start with those and add more as I go.

    1. To debur the nose of the projectile – this can be effective but not for the reason many people think. Aerodynamically the difference in the pressure on the nose is minimal, and likely can be ignored barring any very large burrs or flaps of metal being present. The main deleterious effect on accuracy comes from the mass asymmetry that is created this causes an inconsistency in swerving motion that can cause rounds to fly differently.

    2. Decrease drag – I believe this was referred to as increasing BC above. This effect of blunting a projectile and decreasing the zero yaw drag coefficient has been well documented from 155mm artillery to 5.56mm ammunition. There is an optimum size of the blunted area of around 12% of the caliber of the round. Drag increases as you move above or below this optimum. Assuming a 0.308” round is deviation of 0.009” will be detrimental to ballistic performance. I doubt that hand filing will lead to that kind of accuracy, however I guess it is at least possible

    3. To aid in expansion – if the round started its life as an OTM or FMJ round the nose could be filed down to create a cavity large enough to initiate fragmentation upon impact similar to a hollow point. This would perform fairly well in soft targets at close range while suffering from the above mentioned drag increase.
    4. Penetration – This was incorrectly or at least incompletely mentioned above. Sharpening the point of a round will not increase penetration in a soft target. This is often thought of incorrectly as it can and often does increase penetration in hard targets as long as there is little to no obliquity during the impact event. However this is rarely the case, which is why you don’t see razor sharp points on well designed AP rounds. A blunt tip will actually keep a projectile low yaw once it has entered a soft target and due to cavitation it can penetrate deeper than a sharper projectile depending on the velocity.

    5. Mercury - the myth about filling a projectile with mercury then sealing it with lead or wax to create an “exploding bullet” has existed in Hollywood for years and has been tested in practice to yield results that are disappointing at best. It can be noted however that the mercury would create a fragmenting poisonous slug that if the projectile did initiate fragmentation would cause a lot of tissue damage as well as make sure the target was incapacitated through the poison ( if enough was left in the system).

    Overall it is likely used by the film maker to give the impression that the character knows “secrets” about long range assassinations and must hand craft his projectiles in order to accomplish the objectives of the mission…blah blah blah
    Aero-Ballistic Research Scientist

  6. #26
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    Default Re: Why would one file the tip of a bullet?

    If Clooney was filling the tips with mercury, he was looking for an "exploding" bullet terminal effect. This "mercury-filled bullet" thing is actually an old standby in Hollywood to ramp up the action, like pistol shots blowing legs off (as in "The Punisher") and the all-time fave, the single shot that blows up the gas tank. In the 1970's movie "The Day of the Jackal" the assassin treats all his projectiles this way to . The incompressability of mercury (theoretically) causes the bullet to, in effect, explode on impact with the target.
    There are two problems with this.
    First, regarding accuracy, adding a liquid center to a spinning high velocity projectile may destabilize it to the point that it precesses like an out-of-balance washing machine on the spin cycle...and if the filled bullets don't weigh within, say, a tenth of a grain of each other, they won't fly consistantly, also blowing accuracy to hell.
    Second, with a home-made exploding bullet like this, there's no way to predict how much penetration will occur before the bullet flies apart. It may perform as expected, or it may blow up at or near the surface, causing a painful but non-lethal crater.

  7. #27
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    Default Re: Why would one file the tip of a bullet?

    It was also shown in JAWS.
    Owner Trigger Time LLc 01 FFL/NFA Saylorsburg, PA. Sales/Service/Transfers/Training
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  8. #28
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    Default Re: Why would one file the tip of a bullet?

    Quote Originally Posted by surbat6 View Post
    If Clooney was filling the tips with mercury, he was looking for an "exploding" bullet terminal effect. This "mercury-filled bullet" thing is actually an old standby in Hollywood to ramp up the action, like pistol shots blowing legs off (as in "The Punisher") and the all-time fave, the single shot that blows up the gas tank. In the 1970's movie "The Day of the Jackal" the assassin treats all his projectiles this way to . The incompressability of mercury (theoretically) causes the bullet to, in effect, explode on impact with the target.
    There are two problems with this.
    First, regarding accuracy, adding a liquid center to a spinning high velocity projectile may destabilize it to the point that it precesses like an out-of-balance washing machine on the spin cycle...and if the filled bullets don't weigh within, say, a tenth of a grain of each other, they won't fly consistantly, also blowing accuracy to hell.
    Second, with a home-made exploding bullet like this, there's no way to predict how much penetration will occur before the bullet flies apart. It may perform as expected, or it may blow up at or near the surface, causing a painful but non-lethal crater.
    LOL, I don't disagree with what you're saying about adding mercury to bullets and effects that it might. I disagree with one thing that you and others are saying in this thread. People keep saying "if a bullet isn't within .1 (1/10th) of a grain of each other, accuracy if blown, etc. LOL, have any of you actually weighed every single bullet that you shoot or reload? MOST bullets that people shoot are NOT within a tenth of a grain of each other, or even of the weight that they say it is. Lots of people over the years have NEVER had a problem with accuracy out to 1,000 yards (or further) with Sierra Match King bullets. Lots of people, including the military, do NOT weigh and sort their bullets before loading, and have better accuracy than most people. You'd probably be surprised at the variance in their weight, from lot to lot.

    I do weigh sometimes weigh bullets and sort a box by weight in tenths of grains, and over the course of several boxes. I've sat there and helped friends do it, and then sort those further by meplat, ogive lenths, etc. Even on high quality match grade bullets, unless you're talking lathe turned solids, about the BEST that you're going to get on a box of bullets if for them to be a tenth of a grain of what they're supposed to be. We're talking unloaded bullets (not ammo) that are over 40 cents apiece, and 1/10th of a grain is about as good as you can hope for and expect. If you want something closer, you're going to start having to look at lathe turned solids. The other important thing to remember is that weight isn't even close to all that matters, and some people putting way too much important on variation in a tenth of a grain from their weight, when other factors are just as or more important.

    In reality, most people don't shoot far enough to notice the difference in a tenth of a grain of variance in bullet weight. Most people don't shoot far enough to notice ANY difference in a tenth of a grain variance in bullet weight. Even people that are shooting long enough to notice a difference, most can't read the wind well enough to notice the different of .1 grain variance in bullet weight. I know that I can't read the wind well enough to notice a difference between say a 190 grain bullet and a 190.1 grain bullet. I can shoot well enough to notice a difference of .1 grains in powder charge, but NOT in bullet weight. For some loads, especially when trying to keep your SD's down on a load, .1 grains of powder can make a difference.

    So while I agree with the premise that adding mercury to a bullet could cause it to fly incorrectly, yaw, etc. I think that the variation of .1 grains has almost no effect on the situation. Most people can't shoot well enough to be concerned about bullet run out, .1 powder charges, neck concentricity, neck tension, etc, etc. So I'm sorry, I just don't think that most people will notice any sort of difference in .1 grain difference from one bullet to the next. I hear all the time on this forum about people who's rifles shoot "1 hole", or people that "consistently shoot 1/2 moa groups or better" (sometimes even less than a third or quarter inch). I very rarely hear of those people weighing bullets to see if they're within .1 grains of each other. Go weigh a box of SMK's, which are what Federal Gold Metal Match bullets are loaded with, bet you find a lot more variance than .1 grain.

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