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Old August 17, 2013, 10:50 PM   #1
BuckRub
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Here's a question

I know I read this in alot of different ways but to keep it simplier, If you used the same gun (Glock 22) reloaded 135 grain bullets using Bullseye powder right between min and max and did same with a 180 grain bullet using bullseye and loaded them right in the middle. When comparing the two which should you get a more felt recoil ? Lighter, heavier or basically same. Remember same gun, same powder, both loaded in the middle between min and max and everyone knows there will be more powder in lighter bullets. Take your best shot.
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Old August 18, 2013, 12:26 AM   #2
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It's even simpler than that. Recoil is largely a function of bullet weight. Yes, I know there's going to be multiple posts following this one getting into the minutia of recoil physics and all the sub-factors, etc. etc. etc.

But at the end of the day, bullet weight plays - by far - the biggest role. Yeah, you could probably load up that 135g bullet real hot and get it to recoil more than the 180g slug, but you would have to go on the extreme of the loading scales.
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Old August 18, 2013, 02:13 AM   #3
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Within the same cartridge, I agree with the previous post. But to me (others may differ) a 357 mag 125 grain bullet at 1500 fps has worse recoil than a 45 Colt 250 grainer at 1000.
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Old August 18, 2013, 03:15 AM   #4
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The different weight of powder is a result of keeping the pressure on the same level, it doesn't concern the recoil.
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Old August 18, 2013, 05:50 AM   #5
WESHOOT2
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ain't just the bullet

The formula for recoil includes the weight of the charge (because it has weight and mass, ay?), too.
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Old August 18, 2013, 09:45 AM   #6
BuckRub
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C'mon we're allready starting to get off. Talking bout 357's and such.
Ok say for the 135 grain with 7.3 grains and 180 grain you have 5.3 grains. Same gun.
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Old August 18, 2013, 12:34 PM   #7
big al hunter
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Quote:
The formula for recoil includes the weight of the charge (because it has weight and mass, ay?), too.
No...not for this particular discussion.
What he is suggesting is that the 2 loads are similar pressures. The weight of the charge has no bearing on recoil if both loads are the same pressure.
If the charge is reduced in a load it will reduce that loads pressure, velocity and recoil. If the pressure is the same and the bullet weight is different, then the heavier bullet will have more recoil but less velocity than the lighter bullet.
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Old August 18, 2013, 12:57 PM   #8
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Recoil depends on momentum,which is mass x velocity, but using bullet weight is ok for comparisons sake. While powder affects velocity, given all the other variables, you can't use it the way you suggested, especially since you get different load data from different sources.

A heavier bullet with slower velocity will have the same momentum as a lighter bullet at faster velocity if the product of their weight times velocity is equal.

Given that their momentum is equal, a heavier bullet will have less felt recoil because the push of the recoil is a bit slower, so what you feel is spread out over a little more time. It's actually more complicated than that.
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Old August 18, 2013, 01:25 PM   #9
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Quote:
Yes, I know there's going to be multiple posts following this one getting into the minutia of recoil physics and all the sub-factors, etc. etc. etc.
^-- Heh, that was too easy
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Old August 18, 2013, 03:42 PM   #10
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Quote:
A heavier bullet with slower velocity will have the same momentum as a lighter bullet at faster velocity if the product of their weight times velocity is equal.
True, but the momentum is very rarely the same (almost never). Do the math on published load data for factory ammo. You may be surprised.
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Old August 18, 2013, 06:34 PM   #11
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Recoil

Since both rounds are being fired out of the same pistol, then recoil is directly related to the kinetic energy of the bullet as it leaves the barrel. The bullet with the higher kinetic energy (using muzzle velocity) will produce a higher recoil.

The formula for kinetic energy is:



Where:
m=weight of the bullet in grains
v=muzzle velocity of the bullet in fps

The load data for Bullseye powder from the Alliant web site is limited. It only lists max loads and does not have data for a 135gr bullet.

Using data from Reloaders Reference, I have calculated the kinetic energy of a 135gr bullet at 1350 fps is 546 ft-lbs. The kinetic energy of the 180gr bullet at 1015 fps is 412 ft-lbs.

So, at max loads, the 135gr bullet will produce more recoil.

Without published data on start loads, to interpolate muzzle velocity on a mid load, it is difficult (or impossible) to calculate the kinetic energy of the bullets for a mid load. However, based on the max load calculations, my guess is the 135gr bullet will produce a higher recoil than the 180gr bullet.

It would be interesting to collect some chrono data to confirm.

Question for OP...does this answer your original question?

The link below has an on-line calculator for bullet energy.

http://www.firearmexpertwitness.com/...s/calcnrg.html
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Old August 18, 2013, 06:47 PM   #12
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Quote:
Originally Posted by BuckRub
C'mon we're allready starting to get off. Talking bout 357's and such.
Ok say for the 135 grain with 7.3 grains and 180 grain you have 5.3 grains. Same gun.
So, 135 grains of bullet and 7.3 grains of powder, 142.3 grains of ejecta coming out of the muzzle
vs
185.3 grains of ejecta coming out of the muzzle, albeit at a lower velocity

Presumably at the same pressure.

If you think of the pistol as a free object, the only forces acting on it are the pressure on the breechface and the friction of the bullet in the bore. Since, with the heavier bullet, the pressure on the breechface is acting for a longer period of time I would hypothesize more felt recoil with the heavier bullet. As a first approximation.

Second approximation would attempt to take into account the different time-pressure curve. Third approximation would take into account the bullet friction.

Without some sophistcated lab equipment, I think it would be easier to devise an experiment.

Suspend a sled from a pair of sawhorses. Let the sled swing freely. Lay down on the sled with the gun in a Ransom rest (or something similar). Fire off a round and measure exactly how far the sled swings back. With the same shooter (so the sled weighs EXACTLY the same weight as with the first firing) fire off the other round. Which ammo causes the sled to swing back further? That is the one with more recoil, and I bet it will be proportional to the calculated momentum of the bullet and ejecta at the velocities recorded by a chronograph.

Let us know how it works out for you, please.

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Old August 18, 2013, 07:05 PM   #13
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Sure about that?

Quote:
Originally Posted by FtrPilot
Since both rounds are being fired out of the same pistol, then recoil is directly related to the kinetic energy of the bullet as it leaves the barrel. The bullet with the higher kinetic energy (using muzzle velocity) will produce a higher recoil.
I always thought recoil was more related to momentum than to energy. I would not bet the farm on my belief, though, so I thought I would ask how certain you are.


kinetic energy attributable to a 135gr bullet at 1350 fps is 546 ft-lbs.

+((135+8.3)*1350^2)/2/7000 energy--580
+(135+8.3)*1350/7000 momentum--27.6


kinetic energy attributable to a 180gr bullet at 1015 fps is 412 ft-lbs.

+((180+5.3)*1015^2)/2/7000 energy--424
+(180+5.3)*1015/7000 momentum--26.9

Real velocity data might be different, but clearly, if momentum governs recoil, it is closer than if energy governs.

But only objective, empirical measurement will settle the argument. But then we can argue about the objectivity of trying to measure FELT recoil.

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Last edited by Lost Sheep; August 18, 2013 at 07:34 PM.
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Old August 18, 2013, 08:37 PM   #14
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I am not an expert....

However, the research I did indicates that kinetic energy correlates to recoil. Momentum relates to kill power, penetration, and bullet effectiveness.

What I did leave out of my analysis is ejecta. Assuming 7.3 grains of Bullseye for the 135gr bullet and 5.3 grains of Bullseye for the 180gr bullet, and assuming a factor of 1.75 for the gunpowder ejecta velocity, then the energy of the 135gr bullet = 598 ft-lbs and the 180gr bullet = 433 ft-lbs.

When including ejecta, the 135gr bullet, at max load produces a higher recoil.

Here's a link that discusses recoil energy:

http://www.outdoorlife.com/articles/...-recoil-energy

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Old August 18, 2013, 11:04 PM   #15
Lost Sheep
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Certainly, recoil energy equals the energy out the muzzle (as the article you linked states). And recoil momentum also equals the momentum out the muzzle. Which (if either) is a better indicator of felt recoil, I am still unsure.

What I do know is that felt recoil is a quantity that is very hard to measure, even after you control for the weight of the firearm and the shape and cushioning of the grips/stock. I note that a bullet exiting the muzzle at 1015 fps was (probably) in the barrel accelerating a 30% longer time than one exiting at 1350 fps, suggesting the pressure applied to the gun and the shooter was applied over a longer period of time. I have no idea if that translates to more "felt" recoil or less.

By the way, I really liked the first clip in the second video attached to the article. How old is the child, I wonder? Quite an indictment of the gun owner and proof positive that a toddler can shoot. The child even hung onto the gun-remarkable. At least the lady in the last clip who got the hot brass down her blouse did keep the gun pointed downrange though is appears as if it takes her about 5 seconds to get her finger out of the trigger guard.

The first video looks like it was staged by an anti-gun provocateur trying to convince us women are incapable of using firearms and should be "protected" from such dangerous instruments.

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Old August 19, 2013, 07:14 AM   #16
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does to does to nanner-nanner

Quote:
The weight of the charge has no bearing on recoil
Wrong.
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