gun recoil

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

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  1. Roboss

    Roboss Member

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    What exactly is M4s recoil energy. Google gives me some different answers. 3 foot pounds, 4.5 foot pounds and just over 5 foot pounds.

    Also doesnt recoil increase the less rounds are in a magazine?

    What would be the highest acceptable recoil for a standard military automatic rifle to be comfortable?
     
  2. fxvr5

    fxvr5 Member

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    Recoil can be calculated at the following link: http://kwk.us/recoil.html

    I plugged in a couple of numbers; 7 lb gun, 62 grain bullet, 2900 fps, 20 grains of powder. This produces 3.2 ft-lbs of recoil force.

    Yes, as the gun weight decreases as more rounds are fired, recoil increase. It's not a huge difference, but you can plug in gun weights at the numbers at the above link.

    Highest acceptable recoil to be comfortable? Don't know. Most anyone can tolerate an M16/M4. But running up to a 308/30-06 usually results in some complaints.
     
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  3. TimRB

    TimRB Member

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    According to General Hatcher, "back in the day" 15 ft.lbs was considered the upper limit for military rifle recoil energy. An M1 rifle firing M2 is just a shade under that. A typical 12Ga shotgun is well over 20 ft.lbs (hard to quantify, since there is a wide variety of guns and ammo for 12Ga.)

    Tim
     
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  4. bangswitch

    bangswitch Member

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    Many factors affect felt recoil; overall rifle mass, bullet weight, powder load, buffer weight, reciprocal mass of the BCG, type of buffer spring, just to name a few specific to the AR platform. "Comfortable" is a relative term, some don't mind a lot of 'kick', some don't tolerate much at all.

    If you're trying to determine what you want to get, you need to try out several types and go from there.
     
  5. CapnMac

    CapnMac Member

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    And was part of the reason so many places adopted a 6.5 round was that they are so easy to shoot.
    Almost all of those places then changed to a 7.5 sized round, typically to their strategic deficit.

    These things are not absolute. You don't just plug in values from a spreadsheet and make a yay/nay vote thereby.

    Or else no one would field a 7.62nato or 7.62x54r DMR or SAW.
     
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  6. tipoc

    tipoc Member

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    There is another factor as well.
    The formulas for recoil, like this one: http://kwk.us/recoil.html
    are based on the recoil of bolt action rifles and can't take into account the action of self loading, semi automatic or fully auto handguns or long guns.

    That's why the felt recoil of a 1911 Government Model is much less than the felt recoil of a M25 S&W revolver of the same weight as the GM. The felt recoil of the Garand is much lighter than the felt recoil of a bolt action rifle of close to the same weight.
     
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  7. MistWolf

    MistWolf Member

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    What you mean is, "That's why the felt recoil is softer."
     
  8. ericuda

    ericuda Member

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    https://www.chuckhawks.com/recoil_table.htm

    Decent table of what recoil is vs different cartridges.

    Magazine fill has zero effect but maybe adding to weight. The lighter the gun in general the more the felt recoil.
     
  9. HowieG

    HowieG Member

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    Guns with gas actions, or guns with slides and springs like the 1911 absorb/soften some of the recoil operating the action.
     
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  10. HowieG

    HowieG Member

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    Recoil tolerance is a hugely individual thing with a large number of variables. Body weight and type plays into it and so does age (believe me on that one, lol). A tall skinny guy probably isn't going to like that 458 Magnum as much as a shorter stocky guy.
     
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  11. jmr40

    jmr40 Member

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    Recoil can be mathematically calculated if you have these 4 bits of information.

    * Muzzle velocity of the projectile. This may be impossible to determine exactly unless you have a chronograph. But you can get pretty close looking at ballistic charts.
    * Weight of the projectile in grains
    * Weight of the powder charge. This may be impossible to determine exactly with factory loads, but you can get pretty close by looking at loading manuals.
    * Weight of the firearm.

    Once you have that info plug the numbers into a recoil calculator.

    ShootersCalculator.com | Recoil Calculator

    The recoil from an AR could vary considerably because rifle weight can vary significantly. Bullets can be had from 40 gr to 90 gr, and velocity can vary significantly, but I generally quote around 5 ft lbs. Most people will never notice the difference of anything less than 2-3 ft lbs. For instance a typical 308 will have around 15 ft lbs of recoil whereas a 7-08 is around 14 ft lbs. No shooter will ever be able to tell that difference. But a 243 or 30-30 is closer to 11 ft lbs. That is enough for most shooters to start to notice.

    In theory you'd get more recoil as the magazine gets lighter. But the difference is so small that no one would notice.

    Then there is recoil velocity. Guns with similar recoil, but shooting heavier bullets will recoil slower. A good example is 35 Whelen with 225 gr bullets vs a 300 WM with 180 gr bullets. The actual recoil is the same. But most shooters find the 35 Whelen more comfortable since the recoil is spread over a longer period of time. Granted only a tiny fraction of a second, but it can be felt.

    Semi-auto shotguns and rifles spread the recoil out over longer periods of time due to the gas system. Same principle as a recoil pad. Even recoil operated semi auto handguns do the same to a smaller extent.
     
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  12. MistWolf

    MistWolf Member

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    Soften, yes. Store, yes. Lessen, no. The principle of "For every action, there is an equal but opposite reaction" applies to the moving parts within a firearm as well as to the firearm itself.

    When slides, bolts or carrier groups are pushed back by recoil or gas, there is an equal but opposite reaction pushing forward. The energy isn't absorbed and dissipated by springs, it's transferred and stored in the spring until released.

    When released, the spring pushes the slide, bolt or carrier group forward. In response, the reaction pushes to the rear.

    None of the dissipates recoil. It simply redirects and delays part of it. This has the benefit of stretching out the recoil over a longer period of time so it feels softer.

    There are three basic types of recoil.

    First is Free Recoil, which is the recoil generated by the firearm when fired. The factors for calculating free recoil is weapon mass, payload mass including mass of the gun powder, muzzle velocity and the velocity of the gas exiting the muzzle. This generates a number that's the same regardless of action type.

    The second is called (if I recall correctly) recoil energy. It's simply how much energy the cartridge itself generates before transferring recoil to the firearm. I don't remember what factors are used to figure that out.

    The third type is Felt Recoil. Many factors affect how recoil feels- attack, sustain and fade; stock shape; buttpad type; clothing worn by shooter; shooter sensitivity to recoil; shooting position and so on. The feel of recoil can be radically changed without increasing or decreasing it.

    A 10 pound bolt action 30-06 with a wide, soft recoil pad, it will generate the same free recoil as a 10 pound bolt action 30-06 with a half inch wide butt with a steel plate. Guess which has softer felt recoil?

    Guess which rifle will have softer felt recoil if the half inch wide butt rifle is rechambered to 243? My money is the 30-06 will have softer felt recoil. Although the 243 with the narrow steel plate butt generates less free recoil, it will be much more painful to shoot.
     
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  13. HowieG

    HowieG Member

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    You are certainly correct except I didn't say dissipate and absorb/store is the same thing as far as I am concerned. Springs absorb energy for later release. In this case, the release comes quickly. The key is it keeps you from absorbing the recoil all on your own.
     
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  14. Roboss

    Roboss Member

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    How much higher is the recoil of 6x45mm 70 grain bullet at 3000 fps as opposed to the 62 grain bullet from M4?
     
  15. MachIVshooter
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    MachIVshooter Contributing Member

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    This is an important consideration, especially when you're talking sporters in medium bore magnums like the RUM and Weatherby rounds. The free recoil energy of a .375 RUM or .378 Weathrrby may be similar to .458 win mag or Lott, but it's much faster. My 7.5 pound stainless synthetic 700 BDL in .375 RUM was one of the most fierce recoiling rifles I've shot before I suppressed it, would rattle teeth and give headaches. Most people who tried it had no interest in firing it a second time.
     
  16. JCooperfan1911

    JCooperfan1911 Member

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    The Italians and Japanese used a 6.5mm round at the start of the war.

    As time progressed, they found they were not at all effective and both nations independently switched to caliber .30 cartridges.

    Now we are back in the same boat with the 6.5 Creedmoore. Sorry but I’ll stick to what is proven effective, .30-06 or .308.
     
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  17. MachIVshooter
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    MachIVshooter Contributing Member

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    Well, technically .29 caliber for the Carcano. 7.35x51 uses oddball .298" bullets.

    There's nothing wrong with 6.5mm caliber, but it's terminal effectiveness in the world wars was handicapped by the heavy, rather slow moving and non-expanding round nose bullets that behaved rather like ice picks. Smaller bullets need expansion and/or higher velocity to be as effective as larger ones. The 1899 Hague prohibits expanding bullets, and discovering the efficacy of high velocity small bores was a few years off, so the switch to ~.30 cal was the decision.

    It would have been quite different if the Carcano action had been strong enough and the powder technology mature enough to drive 130 gr. spitzers at 2,800+ FPS rather than the 162 gr. RN at a sedate ~2,200 FPS MV. The 6.5 Jap was a bit faster with a 139 gr. bullet, but still a bit sluggish for being effective with FMJ.
     
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  18. Riomouse911

    Riomouse911 Member

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    I haven’t studied it, but did the Italian/Japanese switch over because the 6.5mm round wasn’t as effective an an anti-personnel round, or was it logistically easier to make-ship-use one 7.7mm round (Japan) that could be used in rifles and machine guns? (I believe Italy used 6.5mm in their ground machine guns through the war but Japan didn’t.)

    Just wondering...:)

    Stay safe.
     
  19. MachIVshooter
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    MachIVshooter Contributing Member

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    The Japs developed the 7.7x58 after witnessing the efficacy of the 8x57. Consolidation logistics may have played some role for the Japanese, but they also made 3 different variants of the 7.7x58, so it would seem it wasn't a priority:

    "While the round chambered by the Arisaka rifle used a rimless case, rimmed and semi-rimmed variants were produced for use in some Japanese machine guns. This machine gun ammunition is more powerful, and the altered rim is meant to prevent it from being chambered in a rifle."

    Though the Italians did use 6.5 in the LMGs that were more of a SAW like the BAR, they used the 8x59 Breda in their standard MGs, so that was probably not a factor there, especially considering that ammunition was shipped on stripper clips for the Breda 30 and en bloc clips for the Carcano rifles. Poor terminal performance is the cited reason for the switch from 6.5x52 to 7.35x51.
     
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  20. Deanimator

    Deanimator Member

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    Before a layoff, subsequent change in work hours and drastic cut in wages made shooting a rifle here impossible, I regularly shot a .30-06 bolt gun with 200gr. Matchkings over a stiff charge of Hodgden 4350. I would do this for an at least one, if not two NRA long range courses of fire.

    I find that my 16" AR carbine has no felt recoil worth mentioning. I don't even use the term "recoil" and 5.56x45mm in the same sentence.
     
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  21. Deanimator

    Deanimator Member

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    The rimmed 7.7mm round was actually .303 British, used mostly in Vickers and Lewis derived aircraft guns used in IJN aircraft such as the Zero, as well as a few IJN small watercraft. The Army Air Force eventually switched over to 7.92x57mm, although I doubt completely, as the Japanese logistical system was what the Brits call "a nonsense".
     
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  22. MachIVshooter
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    MachIVshooter Contributing Member

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    Yes, a direct copy, but loaded hotter as I understand it; you would not want to use 7.7x56R ammunition in a SMLE.
     
  23. CapnMac

    CapnMac Member

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    Well, to be really specific, the issue was effectiveness in machine guns, light and heavy. For full auto fires, not individual rifles.
    Both nations were committed to only having a single round in the Supply chain, even though that failed miserably.

    The need to be able to have ammo that is effective in full auto fires at beyond (typical) rifle range is entirely behind the "why" of DoD adopting a new 6.8 and a SAW to deliver it. It's a steep commitment--it hinges on being able to deliver three different ammo to Rifle Companies to demand (four calibers at the Battalion/Regiment level).
     
  24. lysanderxiii

    lysanderxiii Member

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    The energy of free recoil and recoil energy are the same thing.

    I think the second one you are thinking of is "Recoil Impulse", this is just the recoil energy divided by the time over which it acts. This has a high correlation to the rather subjective "felt recoil".

    There is also "Recoil Velocity", which is the velocity the gun would have if completely unrestrained, and is just the calculated from the momentum of the bullet and gas being equal to the momentum of the gun.
     
  25. army_eod

    army_eod Member

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    Chuck Hawks tables are good. Also look at what mitigation can be had with a muzzle brake.
     
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