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The effect of a heavier weight bullet?

Discussion in 'General Gun Discussions' started by BruceRDucer, Aug 26, 2008.

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  1. BruceRDucer

    BruceRDucer Member

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    /


    The effect of a heavier weight bullet?

    Is: (1) Less recoil? (2) More Recoil?

    (3) There's more to it.

    :uhoh:
     
  2. esmith

    esmith Member

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    As a general rule, the heavier the bullet, the more recoil you will feel. There are more factors that influence felt recoil, barrel length, gun weight, etc.

    One of the Newton laws state that every reaction has you know the equal opposite reaction. Therefore something with more mass will have more momentum, or drag going in both directions, than something with less mass. I think.

    If you want another example take a medicine ball and throw it away from your chest and notice the force pushing you backwards. Then take a ping pong ball or something lighter and do the same thing. You will notice a HUGE difference in backwards momentum pushing you back with the medicine ball than something lighter. I suppose you can say there is more recoil with the medicine ball if you were to try and describe it in terms of firearms.

    Im not a physics professor so don't call me out on using wrong terms or whatever.
     
  3. General Geoff

    General Geoff Member

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    (3) there's more to it.

    You have to weigh bullet weight and velocity, and especially the mass of the gun, as well as to a lesser extent powder burn rates to really determine relative recoil.
     
  4. Sylvan-Forge

    Sylvan-Forge Member

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    Here's a formula for 'Recoil Energy' :

    Recoil energy in foot-pounds (ft-lbs) =

    (Pw x Vp + 4700 x Cw)^2
    .........64.348 x Fw

    Pw = Projectile weight in pounds. (Divide grains by 7000).

    Vp = Velocity of projectile at the muzzle in feet per second.

    Cw = Charge (powder) weight in pounds. (Divide grains by 7000).

    Fw = Firearm weight in pounds.



    Example :
    124 grain bullet/7000 = 0.0177
    1095 f/s muzzle V
    4.6 grains of powder/7000 = 0.00066
    2.1 lb. pistol


    (0.0177 x 1095 + 4700 x 0.00066)^2
    ..............64.348 x 2.1

    =

    (19.3815 + 3.102)^2
    ........135.1308

    =

    505.508
    135.1308

    =

    3.7409 ft-lbs of recoil


    .
     
  5. jakemccoy

    jakemccoy Member

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    Muzzle energy is the most important factor for perceived recoil. While heavier bullets may have more momentum, heavier bullets of the same caliber and same gun tend to have less muzzle energy. Less muzzle energy typically translates into less perceived recoil.

    Analyze your physics equations. Better yet, just go out to the range and experiment. You'll see.
     
  6. Ridgerunner665

    Ridgerunner665 Member

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    As a general rule...all other factors being equal (gun weight)

    The more weight that you're pushing through the barrel (bullet and powder), the more recoil you get.
     
  7. Sylvan-Forge

    Sylvan-Forge Member

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    'Felt Recoil' can be quite subjective.

    Several factors to include the time it takes the projectile to leave the muzzle, pressure curve, how the firearm fits the shooter, bore axis, wrist/hand strength, musculo-skeletal geometry and weight of shooter all factor in.

    One shooter may find a fast 95gr 9mm bullet recoils more than a slower 147gr
    one does while another may 'feel' the opposite way, even though the muzzle and recoil energies may be near the same.


    Often you will hear reported that the fast/light high pressure snaps while the slow/heavy low pressure shoves.

    YMMV.

    .
     
  8. loop

    loop Member

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    Recoil is the least important factor in choosing a heavier bullet over a lighter bullet.

    If recoil in a given caliber is a problem then you need to choose another caliber.

    Ballistic coefficient, sectional density and velocity are much more important factors.

    Ballistic coefficient is the bullets ability to cut through the air (as brief as I can make it). Sectional density determines its ability to hold together on contact.

    In general heavier bullets have higher coefficients and more sectional density that lighter bullets. They also, at longer ranges, have better trajectories.

    Further, in handguns especially, heavier bullets hit higher on the target at shorter ranges than lighter bullets. Lighter bullets also fall off the chart much faster at longer ranges. IOW, they lose their velocity more quickly.

    Also, because the sectional density (length of the bullet) is longer in heavier bullets there is more surface area in contact with the rifling, which improves accuracy.

    These are the factors to consider when looking at bullet weight. Recoil shouldn't be a factor.
     
  9. dogma512

    dogma512 Member

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    Many people feel that the subjective recoil of heavier bullet weights in the same caliber is more manageable. This has been my experience as well.

    200gr .40 slugs are very popular with limited class USPSA shooters that want to make major power factor (which is essentially calculated as momentum with funky units) but still have the most controllable recoil possible.
     
  10. bogie

    bogie Member

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    Strikes me as being one of "those" formulas...

    It assumes I have the same recoil from 42 grains of 4350 in my .308 as I would with 42 grains of AA2230.
     
  11. Vern Humphrey

    Vern Humphrey Member

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    Momentum is the most important factor in recoil. The momentum of the ejecta (bullet and powder) equals the momentum of the gun.
     
  12. jakemccoy

    jakemccoy Member

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    You may be talking about comparing different weights of different calibers. For most people, muzzle energy is the most important factor when comparing different bullet weights of the same caliber, same brand, same gun. If we were to go out to the range and compare the different weights of .40 caliber bullets from Double Tap, I'm confident that 99 out of 100 people would say 135 gr has substantially more felt recoil than the 180 gr. It's not even close.
     
    Last edited: Aug 27, 2008
  13. Vern Humphrey

    Vern Humphrey Member

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    We're talking about recoil. The key element in recoil is momentum.
     
  14. jakemccoy

    jakemccoy Member

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    Actually, we're talking about perceived recoil at the range, not recoil derived from physics equations. I guess you just want to ignore actual experiments at the range with different weights of the same caliber, same brand, same gun.
     
  15. Vern Humphrey

    Vern Humphrey Member

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    If we're talking about perceived recoil from the same gun, then momentum is clearly the calculation we want.

    From the same gun a load that generates more momentum will be perceived as having more recoil than a load that generates less.
     
  16. sqlbullet

    sqlbullet Member

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    Bruce, as is indicated in the thread, there is more too it.

    However, utilizing a simple scenario, we can assume the only change is the weight of the bullet. We have a 'magic' powder that always produces the same velocity from a given charge regardless of projectile mass. We assume we are using the same gun, and all other forces are negligible.

    Recoil is due to Newtons Third Law -"All forces occur in pairs, and these two forces are equal in magnitude and opposite in direction." In this case we are talking about the preservation of momentum.

    momentum = mass X velocity

    Therefore, as mass increases, so does momentum. The paired force to the momentum of the bullet (and expelled charge) is recoil, and it must be equal and opposite. Since the gun and all other variables in our simple example are the same, free recoil must increase.

    As Jakemccoy has pointed out, lighter bullets tend to produce more kinetic energy than heavier bullets. However, this does not translate to more free recoil, since as Vern Humphrey correctly states, recoil is preservation of momentum, not energy.

    kinetic energy = 1/2 mass * velocity^2

    As you can see, the formula for energy is heavily weighted to velocity, since it's input has a geometric increase on the output. Therefore, smaller bullets will generate more energy as there velocity has a huge impact.

    You can evaluate yourself easily how much a bullet weight change will affect free recoil, if you know the velocity. For instance, using Double Tap data for 10mm (yes, I am one of those guys):

    135 grain bullet at 1600 fps = 216000 grain feet/second
    230 grain bullet at 1120 fps = 257600 grain feet/second

    The 230 grain bullet will generate 19.3% more free recoil than the 135 grain bullet in these loads. ((257600-216000)/216000 = .19259...)

    Perception of free recoil is a matter of psychology, ergonomics and kinesiology. Each person decelerates the weapon at a different rate. The longer it takes you to slow the weapon, the less percieved work is done (like using a hoist to raise a motor, same work, over a much longer period means it feels lighter).
     
  17. jakemccoy

    jakemccoy Member

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    My experiments clearly indicate that energy is the culprit.

    For normal people in the real world...

    Perceived Recoil = How much the bang makes you want to say, "Whoa, I can't quite control that."

    Again, I'm talking about different weights with the same caliber, same brand, same gun.
     
  18. Vern Humphrey

    Vern Humphrey Member

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    Your experiments are incorrect. Recoil is a factor of conservation of momentum, not conservation of energy.
    Consider this; A .220 Swift firing a 55 grain bullet at 4000 fps develops 1942 ft lbs of muzzle energy. A .45-70, firing a 405 grain bullet at 1300 fps only develops 1518 ft lbs of energy.

    Yet the .45-70 kicks a lot harder!
     
  19. jakemccoy

    jakemccoy Member

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    Vern,

    It sounds like you have no experiment with same caliber, same brand, same gun. If I were answering a question on a physics exam, I'd say momentum is the culprit. In the real world, the following definition is easier to grasp...

    Perceived Recoil = How much the bang makes you want to say, "Whoa, I can't quite control that."

    Put down the equations for a second. Go out and buy different weights of the same caliber from Double Tap. Then, let a friend shoot the rounds from the same gun without clouding your friend's mind. Ask your friend which bullet has "more recoil." My money goes on the lighter bullet. Of course, you're also free to just give me your money from such a bet.

    -Jake
     
  20. jakemccoy

    jakemccoy Member

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    I hope you realize that scenario doesn't really exist in the real world with the same caliber, same brand, same gun.
     
  21. MTMilitiaman

    MTMilitiaman Member

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    jakemccoy

    He's mistaking actual recoil for perceived recoil. You're mistaking theory for fact.

    Actual recoil is relatively simple to calculate and as mentioned, relies primarily on momentum.

    Perceived recoil is quite a bit more subjective. Some people prefer a slower recoil impulse, even if it involves disruption of more recoil forces. Others prefer a sharper recoil impulse. Stock shape also affects perceived recoil. As an example, I've introduced several new shooters, and my experiments have led me to the opposite conclusion regarding perceived recoil--energy is the least important factor, and the average shooter will be more impressed by how much the gun moves them, which is almost solely determined by momentum.
     
  22. Vern Humphrey

    Vern Humphrey Member

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    What makes you think I haven't done that?

    I have loaded .45 ACP in every weight from 165 to 230 grains. I've done the same with .45 Colt, but gone up to 300 grains. I've done that with many other cartridges.

    In the same gun, the load that develops more momentum will produce more perceived recoil -- even if kinetic energy is actually lower.
     
  23. jakemccoy

    jakemccoy Member

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    We're proving that perceived recoil is based on the individual.
     
  24. BruceRDucer

    BruceRDucer Member

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    Thanks all for responding.

    So according to what has generally been affirmed, (but not always in every scenario) if I shoot a 30-06 rifle (the actual case) with a 150 grain bullet, chances are that I might "perceive" more recoil than with a 180 grain bullet?

    But people are also saying that this perception of recoil can be affected by velocity, and probably the physical characteristics of the rifle, such as its WEIGHT, BARREL LENGTH, BARREL DIAMETER, etc?

    :)

    As I understand this, it is also being said that a heavier 180 grain round, can CONSERVE the MOMENTUM, thus producing significant recoil that way as well. Is this the general idea? That it isn't as simple as some like to think?

    /
     
  25. Vern Humphrey

    Vern Humphrey Member

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    To some extent. Shooter A may find a certain gun and cartridge unpleasant to fire, and Shooter B will not be bothered by it.

    But if we change the load to produce less momentum (even if kinetic energy goes up), both will agree it "kicks less."
     
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