Does felt recoil follow...

Discussion in 'Handloading and Reloading' started by Bill M., Sep 3, 2022.

  1. Bill M.

    Bill M. Member

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    I know the power factor is momentum. wt times velocity. I know that free energy is mass times velocity squared. Which do you think most accurately predicts how a handgun will feel when you shoot it?

    For my .41 Mag I had some Trail Boss loads that felt and shot pretty good. Around 850 fps. I made some Clays loads that the book velocity was only about 30 fps faster. The Clay loads feel a lot snappier. Is it probably just differences in the book velocities from real or is it the squared velocity increase?

    I do not shoot many heavy loads. When I did they do not bother me much. I usually am shooting them with rested forearms and knowing there is recoil and that I am only going to shoot a few. And I am really trying not to flinch and to hit the target. But I do notice differences in my light loads shooting offhand and maybe a difference in how well I shoot them.,
     
  2. Blue68f100

    Blue68f100 Member

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    I normally find a slower powder produces more of a push then a snappy recoil. For me the push is easier to handle. But everyone is different so you need to test for your self.
     
  3. jmorris

    jmorris Member

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    It’s not power factor.
     
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  4. Varminterror

    Varminterror Member

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    Here’s how we get to Free Recoil Energy of a firearm:

    Momentum is conserved, so momentum of the load being fired = momentum of the firearm. This gives us the recoil velocity of the firearm, which allows us to calculate Free Recoil Energy, which is simply the kinetic energy of the firearm.

    So 5.5grn of Trailboss under a 215grn bullet at 850 versus 5.2 grn Clays pushing the bullet to 880:

    Trailboss:

    Load Momentum = 850 * (215 + 1.5*5.5) /7000 = 27.11 lbm*ft/sec <— this momentum is also imparted to the firearm.

    In a 40oz Blackhawk, 2.5lbs, that means a firearm Recoil Velocity of = 27.11 / 2.5 = 10.84 ft/sec.

    This yields a free recoil energy of: 10.84^2 * 2.5 /2 /32.17 = 4.56ft.lbf.


    Clays:

    Load Momentum = 880 * (215 + 1.5*5.2) /7000 = 28.01 lbm*ft/sec <— this momentum is also imparted to the firearm.

    In a 40oz Blackhawk, 2.5lbs, that means a firearm Recoil Velocity of = 28.01 / 2.5 = 11.20 ft/sec.

    This yields a free recoil energy of: 11.20^2 * 2.5 /2 /32.17 = 4.79 ft.lbf.

    4.79 ft.lbf. on the Clays load is only 5% greater free recoil energy than the 4.56 of the Trailboss load. More, but probably not enough for you to notice as actual increase.

    More likely that you’re hearing a difference in report, or playing mindgames with yourself.
     
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  5. westernrover

    westernrover Member

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    I think the ammo factors that affect "felt" recoil the most for a given gun are:
    Recoil velocity (a function of true recoil vs. the gun weight)
    and
    Muzzle pressure (mostly a function of powder burn rate and barrel length) This is not a factor in recoil, but it affects what we perceive considerably.
     
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  6. fxvr5

    fxvr5 Member

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    As noted, the formula for recoil does a fairly good job of predicting felt recoil.

    You can plug the numbers in here: http://kwk.us/recoil.html
     
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  7. Hooda Thunkit

    Hooda Thunkit Member

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    Fast powder = fast climb in pressure = snappy recoil.

    Slower powder = slower climb in pressure = more of a push than a kick.

    That being said, slower powders generally have a heavier (in mass, even in weight) charge than a fast powder.

    That powder charge weight is part of the ejecta, part of the mass being pushed by the expanding gasses.
    Hence, that powder charge itself contributes to a heavier recoil.

    For myself, if I want (example) 1100 fps in a 44 Mag and can use X grains of a fast powder, or X+Y grains of a slower powder to get there, I will generally choose the slower powder.
    It's just more comfortable to shoot.
     
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  8. mdi

    mdi Member

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    Not really an answer. When I was shooting my 44 Magnums a lot I could feel the differences in loads with a fast powder and a mid range to slower powder, with same bullet, approx. same velocity. Bullseye, "snappy, sharp" recoil. Unique hard "bump". 2400, slower "push"
     
  9. GeoDudeFlorida

    GeoDudeFlorida Member

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    The integral of a derivative. We’re looking at two force equations: change of velocity with respect to time and change of inertia with respect to time and distance. The “felt” recoil is purely subjective, not objective. There’s no such thing as an expression for a subjective instance.
     
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  10. denton

    denton Member

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    The amount of force that the firearm applies to you is exactly the rate at which the firearm is losing momentum.

    What we feel is pressure, force per square inch (or square cm, etc) on the bearing surface.
     
  11. Riomouse911

    Riomouse911 Member

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    And, like with long guns, grip fit and composition affect how the recoil feels on your hands.

    DB2106D2-531D-4311-BCF7-751EF7A09876.jpeg

    The bottom grips on my Dan Wessons are not comfy. My middle finger gets bumped with magnum loads and the kick seems to smack my palm with each shot. These are on my .22 because that gun doesn’t kick.

    The wooden grips in the middle are wooden Hogue grips. These feel better to me than the “magna” type factory grips, especially since they keep my knuckle from getting a trigger guard rap with stout recoil. My palm still gets smacked, but not as much.

    The top are rubber Hogues. These feel the best to me since they absorb a bit of recoil where the web of my hand holds the gun. (With the DW 15-2 this holds true with any of my barrel/shroud length combos.)

    Stay safe.
     
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  12. jmr40

    jmr40 Member

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    Felt recoil is very subjective and the human brain is easily fooled. If you convince someone that cartridge "A" recoils more than cartridge "B" they will FEEL more recoil from cartridge "A" even though they may be the same or even less.

    Felt recoil is largely dependent on the shape of the firearm, the grips shape and barrel length. Some firearms will have more muzzle flip, others recoil straight back. The actual recoil can be exactly the same, but how different people perceive it can be very different. Noise fools our brains into believing a louder gun recoils more than one that is less loud, even though they may be the same.

    Recoil velocity effects felt recoil, and if 2 loads have the same recoil energy you can feel the difference in how long that recoil lasts. Generally speaking heavier bullets have slower recoil velocity.

    If 2 loads are within 5-10% of each other most people can't feel the difference. Once you get to 15-20% more recoil it starts to be noticeable and maybe over someone's comfort threshold.

    I prefer to simply run the numbers through a recoil calculation program and trust the math. This takes the human element out of the equation. There can be a considerable difference in the comfort level when shooting the same exact loads from 2 different guns. But that is comparing the guns, not the loads.
     
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  13. Mr_Flintstone

    Mr_Flintstone Member

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    I think recoil impulse is a better predictor of “felt recoil” than energy or momentum, but you also have to figure in factors such as grip-to-hand fit, rotational torque caused by the bore axis height, and gun weight.

    For comparing loads for the same gun (where bore axis and weight are constants), recoil impulse (to me at least) explains how I feel recoil. Impulse = change in momentum = mass x change in velocity = force x time.

    Think about it in terms of a rifle recoil pad. You have the effectively the same recoil energy and momentum with or without the pad, but the recoil feels less with the pad on. That’s not because the pad “absorbs” the recoil, but because it lengthens the time the recoil of the gun takes to come to rest. Looking at the formulas above, if the gun mass doesn’t change and the recoil velocity eventually comes to rest, then the longer it takes, the lower the recoil force will be.
     
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  14. Bill M.

    Bill M. Member

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    Interesting. In my case I was shooting the same bullets in the same gun. Different powders. Slightly different expected velocities. The difference was more noticeable than I expected. Going back with the stouter feeling load slowed down a little next week.
     
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  15. SingleActionAndrew

    SingleActionAndrew Member

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    From my anecdotal arthritic experience, which may be entirely placebo

    All else equal,
    -200gr bullet with 4gr charge Feels easier on my wrists than 185gr bullet with 4.3gr charge
    -slower powder Feels easier on my wrists

    It's not unusual for bullseye shooters say they shoot WST instead of BE or N310 at <=25 yards because the marginal loss in accuracy is worth the perceived felt recoil improvement
     
  16. Mr_Flintstone

    Mr_Flintstone Member

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    Maybe someone with more experience in physics and engineering will come along and clarify, but I think the actual (although difficult to measure by the shooter) reason for the difference in perceived recoil is because of a mathematical quantification called “Jerk” (or sometimes “Surge” or “Lurch”) where j = (final acceleration - initial acceleration) / time. Jerk is defined as the rate of change in acceleration, and is computed using the third derivative of the position function, but that’s not necessary here. What it says is that when something’s acceleration changes very fast we get a big jerk, but when the acceleration changes more slowly the jerk is less.

    It’s been a long time since I used this, but when we use a fast powder such as Titegroup, a bullet will accelerate very quickly inside the barrel with a big rate of change in acceleration in a short time period. When we use a slower powder like IMR 4227 or H110, the acceleration will climb at a slower rate, and over a longer period of time, thus producing a smaller jerk. Likewise on the other side of the gun (although not exactly proportional) we get a larger recoil jerk with fast powders than slower powders. Of course this is assuming other factors such as muzzle velocities of the two loads are equal.
     
  17. __steve__

    __steve__ Member

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    One thing for certain, if the muzzle energy is the same (ex 2000 ft/lbs) for say, a 350 grain (at~1600 fps) and a 600 grain load (at~1200 fps), the 350 grain will feel pleasant compared to 600 grain hand breaker
     
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  18. FROGO207

    FROGO207 Member

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    For me anyway, the weight of the firearm along with the speed of the propellant determine the felt recoil the most. The lighter the firearm the more felt recoil all else being the same. The mind is a wonderful thing sometimes.
     
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  19. murf

    murf Member

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    use a blanket on your shoulder to increase the time change in velocity (newton used delta v, not acceleration in his law of motion) of a high power rifle recoil, or a glove for a pistol recoil. a vehicle shock absorber works this way.

    increase the recoil contact area (gun to hand) to lessen the recoil affect. a bigger contact patch spreads the recoil force over a larger area (makes the blow softer).

    luck,

    murf
     
  20. mmb617

    mmb617 Member

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    I always assumed that the weight of the gun was the most important factor in felt recoil if the ammo was the same, with heavier guns transmitting less felt recoil. But I have an M&P compact .45 that weighs 36 ounces loaded and a 1911 also in .45 that weighs 44 ounces loaded. At least in my perception the M&P has noticeably less recoil than the 1911 when using the same ammo in both.
     
  21. SingleActionAndrew

    SingleActionAndrew Member

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    On 1911s, even with the same exact ammo and total weight of the pistol, in particular the shape of the firing pin stop and how the barrel is fit can significantly affect felt recoil. I would expect a factory 1911 off the rack or with a drop-in barrel to have much more felt recoil than a 1911 with a squared firing pin retainer and a hand fit barrel by a well informed smith.
     
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  22. mcb

    mcb Member

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    Assuming there are no ergonomic issues (ie the gun fits the user properly) then free recoil energy is the best indicator of relative recoil. It takes into account both the cartridge (momentum change) and the weight of the firearm firing it. The military uses free recoil energy to set safe limits for soldiers in training.
     
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