gun recoil

Discussion in 'General Gun Discussions' started by Roboss, Jan 16, 2021.

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  1. lysanderxiii

    lysanderxiii Member

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    In an individually fired weapon, there is only one place the recoil can go - into the person holding the weapon.

    So, unless you have some sort of mechanical support, a bipod, a tripod, a cradle of some sort, you are absorbing all the recoil all on your own.
     
  2. tipoc

    tipoc Member

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    It is true that the mechanical recoil is identical for semiauto firearms as for revolvers, leverguns or bolt action rifles. The measurement for the recoil is the same given the same bullet being fired and the same weight of weapon, all else being equal. The formulas work for both. But the "kick" or felt recoil will be quite different. That is primarily because the recoil spring (or springs) that load the next round distributes some of the kick, or shock, that goes to the shoulder or hand.

    It's also the case that a change in the shape of the stocks on a rifle or handgun can also decrease the felt recoil. It does not change the veracity of the mechanical formulas for recoil. It does make them, the formulas, less relevant for an individuals choice of rifle or handgun, in most cases.
     
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  3. army_eod

    army_eod Member

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    I will be zeroing my 300 Wby mag tomorrow. Weighs 8.5 lbs and wears a muzzle brake. Recoil report after.
     
  4. denton

    denton Member

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    Lysanderxii has the physics right. Just adding some practical numbers to his discussion:

    A 30-06 of normal weight, firing a 180 grain bullet, and suspended so it can freely recoil, accelerates backward at about 500g (your 1 pound scope thinks it weighs 500 pounds, directed along the direction of the barrel). But it only does this for a very short time, a bit more than a millisecond. In the time it is being accelerated, it travels only about 1/8", just enough to start compressing the muscle tissue in the shooter's shoulder, similar to free recoil. After that, the event of interest is the rate at which the rifle is brought back to rest.

    What matters to the shooters shoulder is the force per unit area that the butt transmits to the shoulder. And force is the rate of change of momentum. So what matters is how much momentum the rifle has, and how quickly that momentum is brought to rest. The longer you can spread that event out, the less force on the shoulder. That is how a recoil pad works, and it is why we can tolerate more recoil if our shoulder is free to move.
     
  5. MistWolf

    MistWolf Member

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    Felt recoil isn't about more recoil or less recoil, it's about sharper or softer recoil. Spreading out the recoil doesn't make it so less force is applied to the shoulder, it spreads out the time the force is being transferred.
     
  6. denton

    denton Member

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    Force is exactly the change in momentum divided by time. Twice the time = half the force.
     
  7. Pete D.

    Pete D. Member

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    This^^^^^^.
    There are two types of recoil....free recoil and felt recoil. Free recoil is calculable. Felt recoil is not.
    Formulas give you free recoil figures. Felt recoil, on the other hand, is affected by a multitude of factors. Some are mentioned in previous posts.
    There are even more and they all make a difference. A big set of factors is often left out......the shooter. Size, weight, body type are all factors. Experience is a biggie.....does the shooter hold the gun properly, position the head properly, etc.? How much experience does the shooter have with the particular firearm and load? Give a Garand to someone who has shot nothing but .22s and their reaction to recoil will be different than someone who has used the Garand to shoot high power matches for thirty years.
    Position matters.....shooting a heavy kicking gun from the bench is one thing. Shooting the same gun standing is another.
     
  8. FL-NC

    FL-NC Member

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    The recoil on the M4 carbine is negligible.
     
  9. army_eod

    army_eod Member

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    300 Wby vs 5.56 D43A9C14-6566-482B-859F-F27C6391F366.jpeg
     
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  10. HowieG

    HowieG Member

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    A recoil system, spring or hydraulic or friction, is a type of mechanical support. For instance an A5 recoil system using friction rings reduces recoil by converting it into heat and dissipating it into the atmosphere.
     
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  11. TimRB

    TimRB Member

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    This thread has gone crazy. There are people here who actually know what they're talking about. I thought that was specifically prohibited in threads on recoil.

    Oh, the humanity.

    Tim
     
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  12. Terry G

    Terry G Member

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    All this formula stuff! You can simplify it. easily. Wow! This thing doesn't kick at all to Man, this thing kicks like Hell!
     
  13. lysanderxiii

    lysanderxiii Member

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    The laws of conservation of momentum (mv = mv) say otherwise.

    As to energy, the loss of energy is negligible. Even in an artillery recoil system, the rise in temperature is not enough to impact the recoil forces.
     
    Last edited: Jan 24, 2021
  14. MachIVshooter
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    MachIVshooter Contributing Member

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    There's still a time component to it.

    The free recoil is the same, a function of the weapon's inertia vs. the force applied to it by acceleration of the bullet in the bore, and (to a lesser degree) the exiting gas jet. Free recoil calculation is a simple function of gun weight vs. bullet weight, powder charge and velocity. The felt recoil is reduced by, as Denton explained, spreading that impulse out over a longer period, which is what recoil pads and other recoil mitigation systems do.

    And to that end, the reason muzzle brakes and suppressors reduce felt recoil is that they slow & divert that gas jet, which is responsible for a great deal of the felt recoil, since that jet acts on the weapon for a longer period than the initial impulse from bolt thrust that is measured in microseconds. In the case of suppressors, they also increase the inertia by adding weight, so that's a factor too.


    This made me laugh. I know it probably wasn't intended to be humorous, but the vernacular made it so!
     
  15. kimberkid

    kimberkid Member

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    I used sample data for the above mentioned calculator, for a 308 the recoil energy was 11.4
    I know in my HK91, in stock form (hard plastic butt plate), in full-auto it only takes 3-4 rounds before I have to let off the trigger due to muzzle rise, but my shoulder is hamburger after 3-5 strings like that. With my HK21 stock that’s made for full-auto and has a 2-stage heavy recoil buffer and thick rubber butt pad, several more strings aren’t a problem for my shoulder but muzzle rise still is, regardless, it really isn’t anything I’d take out plinking ... HK53 (223) & MP5 (9mm) aren’t a problem for an afternoon of full auto fun.
     
  16. MistWolf

    MistWolf Member

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    But force is sustained for a longer time. The energy from13 ft/bs of free recoil is the same amount of energy whether it's within .01 seconds or spread out over .10 seconds. Just like 500 BTUs of heat is 500 BTUs whether it's applied to 1 gallon of water or 10.
     
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  17. denton

    denton Member

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    I think you are confusing force, energy, and momentum.

    Conservation of Momentum gives us the ability to analyze some otherwise difficult situations.

    Kinetic energy is not conserved. Force is not conserved. Momentum is conserved.

    Remember F=ma? It quickly follows from this formula that impulse (the change in momentum) is force. Force is exactly the rate of change of momentum. If momentum is shed half as fast, the force is half as much for twice as long, always and forever.

    For the curious, momentum is MV. In the formula above, a=acceleration. But acceleration is the rate of change of V. So force = mass x rate of change of V. IOW, force equals the rate of change of momentum. Isaac Newton so declares.
     
    Last edited: Jan 24, 2021
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  18. CapnMac

    CapnMac Member

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    Put the former into an 8# rifle and the latter into an 18# rifle, versus the reverse.
     
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  19. Deanimator

    Deanimator Member

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    Recall a few years ago, the snowflake who shot an AR type rifle in 5.56x45mm who was "traumatized" by the recoil? They made it sound like they were shooting an H&R Handi-Rifle chambered for .950JDJ.
     
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  20. Pete D.

    Pete D. Member

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    This^^^^ is true. Shooter experience is the difference between saying "negligible" and "ouch".
     
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  21. Jeremy2171

    Jeremy2171 Member

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    Three different "mainly" types of 7.7
    7.7x56r which is a copy of .303 and interchangeable.
    7.7x58SR which can be found in the Type 89/92 MGs with separate loadings
    7.7x58 which is the typical T99 load.

    The T92 mg round has a semi-rim to help with extraction purposes..that's it. The prototype T99 rifles were T38s with 7.7x58SR chambered barrels. The army decided the T92 loading of a 206grn bullet at about 2400s was too much recoil for the slight stature jap soldier and they felt the semi-rim could give feeding issues. So they dropped the rim and used the lighter T89 bullet (~182gr) and that became the T99 round as we know it.

    Now...you can interchange the two rounds.. T92 HMGs run T99 ammo just fine. Some T99 rifles will allow the T92 semirim to fit on the bolt face...some won't. The brass is identical except for the semirim. Some people filed the rim off the case...some filed the bolt to remove the lip so they would feed.

    Another comment.. do NOT shoot WW2 jap brass its poorly made and brittle and can split/fail on you. You can still find the 7.7 MG feed strips fairly cheap and they are pretty common compared to regular T99 ammo. You can pull them down and put the powder and projectile in new grafs brass for some cheap plinking ammo. Lots cheaper than Steinel made stuff.
     
  22. Reloadron
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    Reloadron Contributing Member

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    For the truely curious at heart and those who simply like to crunch numbers SAAMI has a short paper on the subject of FRE (Free Recoil Energy). Additionally Hatcher's Notebook devotes quite a bit of information on the subject. Now as to felt recoil? That seems to change. I know 40 years ago shooting my 7mm Rem Mag bolt gun was not as challenging as it is today. Matter of fact I no longer even shoot that rifle. As to handguns my S&W Model 29 in 44 Mag came with wood grips which stung when shooting it. Adding a set of Hogue soft rubber S&W grips made the gun much, much more manageable. Yet, the free energy recoil is the same.

    If anyone would like their very own Free Recoil Energy Calculator you can download one using the link. The download is in a zip folder so just extract it and install it. The little program is for Windows and runs on anything from Win 98 to Win 10. The program is for rifle only! The program uses the formula in the above linked SAAMI Paper. Anyway, it's there for anyone who wants it. :)

    Ron
     
  23. halfmoonclip

    halfmoonclip Member

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    Wow. Too much physics here for me; I'm more of an empirical guy. My '97 Winchester kicks, the M16A1 clone does not. Eleven hundred feet/sec 9s in a P365 are pleasant; the same loads in a 940, more like light magnums. Forty five ACP in a 1911 or a 625, meh, not much difference, but in a Ti 325...
    Oddly, a Garand always felt more like a firm push, an M14 (shot one in basic) felt sharper.
    Then there is technique; a bud in AIT, city kid, shooting an m79; first round hurt a little. Soooooooo, next shot, he held the Blooker away from his shoulder...it of course, got a running start, and knocked Charley right on his ass.
    My own basic rule of recoil; if it kicks too much, don't shoot it.
    Moon
     
  24. lysanderxiii

    lysanderxiii Member

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    TOP 03-2-504A - Safety Evaluation of Small Arms and medium Caliber Weapons sets the following limits concerning recoil energy:

    15 ft-lbs = Unlimited Firing
    15 to 30 ft-lbs = 200 rounds per day per individual
    30 to 45 ft-lbs = 100 rounds per day per individual
    45 to 60 ft-lbs = 25 rounds per day per individual
    Greater than 60 ft-lbs = no shoulder firing

    The method of measuring recoil energy is with the pendulum method, where you suspend the weapon with wires, shoot it and measure how far back and up it goes and calculate the energy from that.
     
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  25. HowieG

    HowieG Member

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    All I can say is google thermodynamics and dissipation. I am certainly not here to teach physics. This is a firearms forum.
     
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