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Muzzel acceleration for sniper rifle

  1. Jan 26, 2010 #1
    Hello

    I am trying to get a ball park number on how many Gs the muzzel of a sniper rifle might experience when firing a round at supersonic speeds. An example rifle is the Sig Sauer Tactical 2 or the Barrett 98B -- an order of magnitude would be very helpful.

    Thanks
     
  2. jcsd
  3. Jan 26, 2010 #2

    minger

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    You can fairly well assume that the bullet is only accelerating while inside the barrel. A quick google/wiki gives the Barrett M98B a muzzle velocity of 3100 ft/s. If you make a decent guess at the barrel length and assume a constant acceleration, the solution should be fairly straightforward.

    edit: As a check for your work I got 17.5 g.
     
    Last edited: Jan 26, 2010
  4. Jan 26, 2010 #3
    If you use the equation

    v2= 2·a·x

    where v = velocity (3100 ft/s), a = acceleration, and x = distance (3 ft), in feet and seconds, then

    a=v2/2·x = (3100)2/(2·3) = 50,000 g's !!!

    Bob S
     
  5. Jan 26, 2010 #4
    The bullet is supersonic leaving the barrel. But I am interested in the muzzel movement as the bullet leaves the barrel. As the bullet leaves the barrel, gases are released. These gases cause the muzzel to move. It is the muzzel movement -- acceleration -- that I want to track-- not to an exact number -- but to an order of maginitude. I want to minimize destroying too many accelerometers before I know what the basic G force is.

    Thanks
     
  6. Jan 26, 2010 #5
    Here is a URL with equations and table for rifle recoil:

    http://www.loadammo.com/Topics/August01.htm [Broken]

    If you assume the total mass of bullet plus gases has a mass of ~250 grains = 16 grams, and the rifile has a mass of 4000 grams, then the muzzle recoil acceleration (not counting the body shoulder support) is

    amuzzle = 16 x 50,000/4000 = 200 g's

    Bob S
     
    Last edited by a moderator: May 4, 2017
  7. Jan 27, 2010 #6

    minger

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    Whoops forgot to square the velocity...small mistake, haha.
     
  8. Jan 29, 2010 #7

    Lok

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    Btw the gases reach speeds of 3 times the bullets at the muzzle, which makes up for almost 50% of the recoil. this kinda doubles your number to 400Gs.
     
    Last edited by a moderator: May 4, 2017
  9. Feb 1, 2010 #8
    You can get a good bit of ballistics information for different "sniper" platforms over here, http://www.snipershide.com/forum/ubbthreads.php [Broken]

    The majority of "sniper" rounds are generally hand loaded so you'll end up having a variety of different muzzle velocities for the same round.
     
    Last edited by a moderator: May 4, 2017
  10. Feb 5, 2010 #9

    sophiecentaur

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    Interesting. It implies that the mass of propellant must be about 1/3 of the mass of the bullet.
    There is a point to consider here: the gases spread out when they emerge from the barrel - only a proportion of the impulse produced will be directed as recoil (the forward component). Also, the gases emerge after the bullet has left so you, presumably get a graph of acceleration with a step change in it. The max acceleration will presumably be whilst the bullet is actually travelling down the barrel.
    200g seems an awful lot but I guess it's only for a short time. The amount of actual share of energy in the recoil is pretty small c/w that of the bullet, on account of the vsquared factor.

    God, I wish you guys would use SI units! Call me old fashioned but. . . "grains" went out with apothecaries over here.
     
  11. Feb 5, 2010 #10

    Lok

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    The value of 50% is empirical, as it is the average recoil reduction of attaching a suppressor to a rifle, which however made stops most of the gases.

    Metric is the future!!! Revolution!!!
     
  12. Feb 11, 2010 #11

    Danger

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    But one uses subsonic rounds with a suppressor, which negates the original loading data. A muzzle brake, on the other hand, works well with full loads.
     
  13. Feb 11, 2010 #12

    Lok

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    Everything works with everything in this case. The results where from a study to promote suppressors, on normal supersonic ammo. They are excellent muzzle brakes, any unlike muzzle brakes their recoil damping refers only to the exhaust gases,which they fully stop, without backward directing.
     
  14. Feb 11, 2010 #13

    Danger

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    Ah, I see. Yes, they are good at pressure absorbtion and recoil reduction, not to mention flash arresting. (I design the things as a side-line... :uhh:)
    I merely mentioned what I did because somewhere in the vicinity of 50% of a gunshot sound is from the sonic boom of the bullet. A suppressor used with supersonic ammo disguises only where the shot came from, not the fact that a shot was fired. Depending upon the circumstances, that can be detrimental to the shooter's well-being.
     
  15. Feb 11, 2010 #14
    https://www.youtube.com/watch?v=vKSI7MQhB0o

    The longest confirmed kill in History. 1.51 miles, that is a long way to hit a human sized target. Robert Furlong is a god amongst men!

    Carlos Hathcock tried to re create this shot in the desert of Arizona I believe and failed because of the weather differences.
     
  16. Feb 11, 2010 #15

    Danger

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    Yeah, Canuks! We're sort of born with the ability that if we can see it, we can hit it. :wink:
    (I give some grudging acknowledgment to the Yank ammo...)
     
  17. Feb 11, 2010 #16

    Lok

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    On long range shots the sonic boom is louder, as the initial shot bang fades while the sonic boom just gets created. Anyway snipers care more about the flash and dust cloud than an average idea of what their position is (especially on long range shots). Suppressors are great at flash, dust cloud reduction and clearly as a blue sky they increase accuracy, plus that it's somewhat gentler on the ears. Besides being clumsy(unless telescoped) and heavy things, they tend to heat the barrel more than normal.

    You design them, nice!!!
    What format of CAD do you have and could you send one?
     
  18. Feb 11, 2010 #17

    Danger

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    I'm afraid that I have no CAD at all. I have a home-made draughting table, but the cleanup crew at my house broke both of the rules off of my draughting machine. If I have to make a solid design, as opposed to my normal pencil and paper sketches, I use whatever version of Illustrator I have available. Currently, that is 6, 8 & 10. I preferred CS, but my ex accidentally dumped a beer into the computer that housed that one. I have Inkscape on this one, but haven't figured out how the hell to use it. On the surface, it looks like Illustrator, but it sure doesn't work the same way.
    My pride and joy, design-wise, is intended for high-power rifles. You can turn it on or off, without removing it from the weapon, to provide either power or quietness. There's a wee bit of overlap available, as well.
    By the way, someone has been snowing you in one regard. Suppressors absolutely do not increase accuracy. They invariably diminish it. They can increase the accuracy of the shooter, due to lack of recoil, flinch, etc., but the accuracy of the weapon suffers. Any good suppressor has an absolute minimum of one wiper that impinges upon the projectile. It won't likely matter at close range, but it sure as hell can make a difference at a hundred metres or more.
     
  19. Feb 11, 2010 #18

    Lok

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    2D is fine in this field, but for more complicated designs CAD is better at dimensioning, weight repartition and overall resistance. I've made a few suppresors myself in CAD and their attachments, though after 2 years nothing got as I pleased.

    Wipes are what is wrong with suppresors these days, they limit # of shots to 1 decimal. Wipes are intended for bullet speed slowdown. Useless with subsonic ammo. And even more useless on rifles with rifle ammo as they wear of in 2 rounds or less. A usual baffle design which if made out of good materials can fire 10000 rounds with little damage and uses no wipes. The thing about baffle only suppressors is that they stop the exhaust that would otherwise influence bullet path. Hot gases flying 3 times faster for 1m with the bullet will do a lot to it's trajectory.
    So I still keep my opinion on accuracy.
     
  20. Feb 11, 2010 #19

    Danger

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    Uh... no. Wipes, of which there is always one on the end, if nowhere else, are meant to contain stray gases and direct them back into the baffle system. The ideal situation, unfortunately, is its own downfall. The simplest wipe is just a neoprene disk with an 'X' shape slit into it with an X-Ecto knife. The 'blow-forward' (gas that leaks past the bullet and exits ahead of it) opens the wipe to allow free passage for the bullet. That can, but doesn't necessarily, prevent physical contact between the wipe and the projectile, but it still sets up a turbulent airflow that can alter the trajectory. It also allows that preceding gas to expand into the atmosphere, which makes a significant noise. A more aggressive end wipe, such as a solid neoprene disk, contains more of the gas, but definitely impinges upon the flight path of the bullet. For maximum quieting, you want at least 3 such wipes at the exit. There's always a trade-off.
     
  21. Feb 12, 2010 #20

    Lok

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    Seems too DIY for a good thing.

    A great way for sound suppression, which is not really my thing, is to port the barrel in several groups. Each group has it's own suppressor chamber so that the gas gets a good expansion while the bullet acts as a plug, no wipes, great accuracy, and the suppressor is telescoped for compactness. The only true downfall is that the heat will influence multi shot accuracy. The russians got it right with their silenced bullets (the ones that leak no gas at all), and the VSS is the definite concept of silent sniper design (heavy bullet subsonic ammo, huge suppressor with ported barrel and multiple chambers and no wipes for long lifetime).

    This design is nothing new as I know the mafia of the 50's used it with long barrel ruger pistols. They just drilled some holes, got a pipe around it and the small 22.LR was more silent than the action.
     
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