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Thread: 9 mm recoil: 147 gr or 124 or115?

  1. #1
    Member randyflycaster's Avatar
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    9 mm recoil: 147 gr or 124 or115?

    Yesterday I shot a box of 115 grain, and I was surprised at the recoil. I don't know the velocity of the ammo. I did some research, and it seems that, as a general rule, the heavier grain the less the recoil. Is this true? And what grain do competitive shooters use?

    Thanks,
    Randy

  2. #2
    Site Supporter JRV's Avatar
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    It’s less about actual recoil and more about feel/slide velocity (perceived recoil). Factory ammo is a wash, purpose loaded match ammo (commercial or hand-loads) is different. By that I mean, there’s a good bit of 124 grain 9mm on the market that’s loaded much hotter than it needs to be in order to mimic NATO spec. And, 147 grain factory ammo tends to hit 950-1,000 FPS, duplicating standard pressure defensive loads, and not necessarily providing the perceived recoil benefits attainable with heavier bullets.

    Heavier bullets leave less case capacity for powder and need a lower overall velocity to make power factor. A subsonic 147 grain load, purpose loaded for match shooting, only needs to go about 870 FPS to ensure it will make 125 PF in nearly all atmospheric conditions, whereas a 115 grain load needs to go about 1,100 FPS to hit the same PF.

    That’s extra slide velocity and report in return, which contributes to a “snappier” feel than a match 147 grain load. Heavier bullets tend to have more of a “pushy” recoil feel.

    You have to test it out for yourself and not presume one particular load will make shooting easier, because the way your gun cycles (slide mass, spring rates) and your own biomechanics dictate how your sights return to point-of-aim. I usually warm up and run Bill Drills when I am choosing between (or trying to get acclimated to) different ammo. Regardless of perceived recoil, your natural tempo and post-shot recovery might provide best results with a particular bullet weight.
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  3. #3
    SHhhh don't let the secret out of the bag

    Factory loads can be an exception depending on load, but if one is loading for a specific power factor (weight X velocity/1000) a heavy bullet requires less powder which makes less gas and has less speed leaving the barrel. So less impact on the shooter.

    Or something like that.

    Most USPSA shooters I know use either 124(125 if coated) or 147. Both can work well depending or what the gun and shooter prefers. Heavier bullets are more reliable when is comes to knocking down steel poppers, particularly big heavy poppers at distance.

  4. #4
    Member randyflycaster's Avatar
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    Great info.

    I should say I don't reload. I've been looking for 147 gr to try it out, but with this ammo shortage I can't find it, and if I buy online I'll get hit with a heavy shipping charge.

    Besides, I was just curious.

    Randy

  5. #5
    Site Supporter ST911's Avatar
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    Quote Originally Posted by randyflycaster View Post
    Yesterday I shot a box of 115 grain, and I was surprised at the recoil. I don't know the velocity of the ammo. I did some research, and it seems that, as a general rule, the heavier grain the less the recoil. Is this true? And what grain do competitive shooters use? Thanks, Randy
    Entirely load dependent, in combination with the gun.

    And lot-to-lot variations in the same sku can be significant in current conditions.
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  6. #6
    Quote Originally Posted by randyflycaster View Post
    ...it seems that, as a general rule, the heavier grain the less the recoil. Is this true?...
    If that were true, everybody would go back to shooting 230 gr 45 ACP.

    There are two types of recoil that a shooter needs to be aware of. Free Recoil and Felt Recoil.

    Free Recoil- This is the recoil of the firearm when fired. There are three factors when calculating free recoil:
    1) Mass of ejecta. This is the mass of the bullet and powder
    2) Mass of the firearm
    3) Ejecta velocity. There are two different velocities
    A) Velocity of the bullet
    B) Velocity of the expanding powder after the bullet uncorks the muzzle. Velocity of expanding gas from smokeless powder is a constant. I forget what it is, but if I recall, it's 5,700 fps.

    Free Recoil is increased when-
    - Ejecta mass in increased (bullet and/or powder mass)
    - Bullet velocity is increased
    - Firearm mass is decreased

    Free Recoil is reduced when-
    - Ejecta mass is decreased
    - Bullet velocity is decreased (Velocity of expanding gas is a constant. It does not increase or decrease.)
    - Firearm mass is increased.

    Getting back to the question above, is it true (free) recoil is reduced with a heavier bullet? The answer is, to reduce free recoil with a bullet of increased weight, the velocity must also be decreased. The velocity must be decreased enough to more than offset the increase in free recoil from using a heavier bullet.

    If a heavier bullet is launched at the same velocity as a lighter bullet, of course, there's an increase in free recoil. A 147 gr bullet at 1000fps is going to kick harder than a 115 bullet at 1000fps.

    The other type of recoil a shooter is concerned with is Felt Recoil. Where free recoil is subjective and its energy can be calculated easily, Felt Recoil is objective and if it could be calculated, it would require more sophisticated calculations. Felt recoil is changed by fit, acceleration and deceleration of reciprocating mass, everything that affects free recoil, unsprung mass to sprung mass, brakes, type of buttpad, how many layers of clothing worn by shooter and even personal preference and mindset. It gets complicated fast.

    One factor as discussed earlier in this thread, is acceleration rate of the bullet. Some rounds feel softer because the payload is accelerated as a slower rate even though they may actually generate more recoil. What this means is, softer recoil isn 't less or more recoil, it's just softer and can be more comfortable. When people say rounds with heavier bullets have less recoil, what they probably mean is, the load feels softer.
    Last edited by MistWolf; 08-22-2021 at 01:13 AM.
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  7. #7
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    Quote Originally Posted by randyflycaster View Post
    Yesterday I shot a box of 115 grain, and I was surprised at the recoil. I don't know the velocity of the ammo. I did some research, and it seems that, as a general rule, the heavier grain the less the recoil. Is this true? And what grain do competitive shooters use?

    Thanks,
    Randy
    It's true that, at a given power factor (bullet weight x velocity/1000), heavier bullet ammo will have less perceived recoil, all other things being equal. It's just that all other things aren't equal.

    Different brands of 115-grain ammo are loaded to different velocity levels, and those levels are ranges rather than specific numbers. European stuff tends to be hotter than American stuff. Manufacturers go with whatever powder they can get a good deal on that delivers velocities in the desired range at safe pressures. Slower powders require heavier charges to get to a given range and also produce more unburnt powder which influences recoil due to increased ejecta (see above post).

    Now that the ammo situation is stabilizing, I'd try different brands and see which you like and stick with that. For most of us, the brand we like is whatever's on sale, and we live with the minor differences in recoil.

  8. #8
    Member randyflycaster's Avatar
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    Then if I am buying factory ammo how do I know which ammo has less recoil?
    Thanks,
    Randy

  9. #9
    Momentum is conserved
    Kinetic energy is not conserved

    Assuming blast and sound are not considered, physical “Recoil” is related to momentum, which is why very fast lighter projectiles will generate far less “recoil”. In terms of handguns it gets more complicated due to physical characteristics of the pistol-operator interface, slide mass, recoil springs, hammer spring or other factors than can either temporize or “absorb” the forces. Time is also a huge factor…the same force over a shorter time period will be perceived as much stronger although by Newton’s 3rd law it’s the same.

  10. #10
    Quote Originally Posted by randyflycaster View Post
    Then if I am buying factory ammo how do I know which ammo has less recoil?
    Thanks,
    Randy
    One way is with the Recoil Calculator- https://shooterscalculator.com/recoil-calculator.php

    Using load data from the Hornady Handbook of Cartridge Reloading (8th Edition) I used the above calculator to calculate the recoil of 147 & 115 gr loads fired from a Glock 17. According to the Glock website, a Glock 17 weighs 2.02 lbs with a full mag and 1.55 with an empty mag.

    Choosing the slowest 115 load (1000 fps) with the lightest powder charge, Free Recoil from a fully loaded Glock (2.02 lbs) is 3.7 ft/lbs. With the heaviest powder charge (same velocity) Free Recoil is 3.55 ft/lbs. Free recoil from a Glock with an empty mag (1.55 lbs) is 2.84 and 3.53 ft/lbs respectively.

    At max velocity (1250 fps) the lightest charge from a fully loaded Glock generates 4.93 ft/lbs of free recoil. Heaviest charge is 4.99 ft/lbs. From an empty mag (1.55 lbs) it's 6.43 & 6.5 ft/lbs respectively.

    A 147 gr bullet at 750 fps from a fully loaded Glock 17, lightest powder charge is 2.56 ft/lbs, heaviest is 2.87. From an empty Glock, it's 3.34 and 2.87. Same from an empty Glock is 3.34 and 3.74.

    147 gr bullet at 900 fps is 3.67 & 4.14 and 4.78 & 3.34.

    At 1000 fps second, we have 4.67 & 5.12 and 6.09 and 6.67.

    You can see that your handgun recoils on the first shot from a full mag than it does on the last shot when the mag is empty.

    When using the above calculator, figure an average powder charge of 5 grains for 115 & 124 gr bullets and 4 gr for 147 gr bullets.
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