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Do you think getting shot with lighter BBs from an an upgraded gun would hurt more, less, or the same?

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Old November 3rd, 2008, 22:17   #1
DonP
 
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UPDATED AGAIN! Do you think getting shot with lighter BBs from an an upgraded gun would hurt more, less, or the same?

(I wanted to make this a poll, but apparently I took too long to type because you only have a 5 minute window. )

Simple question for half-assed science time!

Your gun shoots X fps. Assume X is consistent and high enough that you would maybe think twice about shooting someone at close quarters.

Do you think putting lighter ammo in your gun would hurt someone more, less, or the same? (In other words, would the lighter BB transfer more, less, or the same energy?) Why?


Bonus related topic:

Many people transition to sidearms when getting into close quarters, since most guns nowadays shoot pretty hot. Now, other people bring up the fact that doing it for safety's sake is a little weird since modern gas pistols actually shoot at least as hot as most electric rifles nowadays.

All other things being equal, do you think putting lighter weight ammo (like, .12s) into your gas pistol would help this?



Updated with test results! See this post.



Updated with a small duplicate test using floral arrangement foam, and a penetration test between .12 and .43. See this post.

Last edited by DonP; November 7th, 2008 at 17:53..
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Old November 3rd, 2008, 22:21   #2
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Heavier BB = more kinetic energy. Same as a real bullet.

And not all guns are consistant with delivering the same energy to BBs of different weights.

Case in point, my old KSC USP Compact. It shot 300 fps whether I used .20g or .25g BBs.
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Old November 3rd, 2008, 22:23   #3
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it's been proven that Heavier BBs WILL retain more energy over time and distance compared to a lighter BB, which in return results in more pain.

This is also why reasonably heavier ammo(eg, 0.20g vs 0.25g. Not like 0.20g vs 0.43g) with the same gun has FARTHER maximum and effective range than a lighter ammo. They are also able to take more hop before spinning up into the air compared to a lighter BB.

As for the GBB issue, the thing with gas is that if the BBs heavier, it stays in the barrel a longer period of time than a lighter ammo would. This effect in return gives the gas more time to expand thus producing more velocity. That's why sometimes you would see a gun shooting 300FPS with 0.20g and still shoot 300FPS with 0.25g BBs, it's because the BB stays in the barrel slightly longer.

Last edited by Skladfin; November 3rd, 2008 at 22:25..
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Old November 3rd, 2008, 22:26   #4
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I'd think that lighter rounds would hurt less, or at least, do less damage. Even though the muzzle energy is approximately the same (heavier rounds appear to be slightly better as capturing energy during the internal ballistics phase), the weight of the round itself affects density and momentum.

In theory (my theory, anyways), all else being equal, a heavier (denser) round would hurt more because it would cause more damage. It would do so by both deforming less (less energy loss to elasticity) and penetrating deeper (better retention of its energy during the terminal ballistic phase).
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Old November 3rd, 2008, 22:40   #5
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Kinetic Energy = 1/2 x Mass x Velocity^2

Simplified Kinetic Energy is proportional to the Product of Mass and the Square of the Velocity. So if you have a faster firing gun, the reason it hurts more when you use the same ammo is because there is more kinetic energy, just like you said.

When you fire an airsoft gun, the energy stored when the spring is compressed, in converted into energy carried by the BB. The spring will always transfer the same amount of energy to a BB, so according to the equation above an increase of mass result in a reduction of velocity. Conversely a reduction of mass for an equal amount of energy will result in an increase in velocity. The overall energy of the BB is always the same.

There are two things that affect how much the BB will hurt. First is the amount of energy the BB carries, and the second is impulse. Impulse simply is the amount of force applied over time. A high impulse (lots of energy over less time) tends to "hurt" more, while a low impulse (less energy over lots of time) "hurts" less. To visualize this, immagine a rubber ball, and a steel ball, both the same mass. A rubber ball imparts a lower impulse (less force per unit time) and a steel ball imparts higher impulse (more force per unit time) which is why you'd rather be hit by a rubber ball then a steel ball.

The difference in impulse between different BB weights is negligible if not non-existant since they are made of the same material more or less. Hence the amount a BB will hurt is only based on how much energy the BB is carrying WHEN IT HITS YOU.

This is where BB weights matter. A heavier (or technically speaking a more massive) BB has greater inertia. A lighter projectile will have less intertia and the force of friction/wind will affect it much more. A heavier projetile will have more intertia, and will not be as affected.

Therefore at point blank, both a 0.2g and 0.3g BB should "hurt" just the same. However at a longer distance, a 0.3g BB will maintain its velocity, and hence will hurt more.

I hope this helps you understand why it would hurt more or less .

EDIT: Also, the reason why lighter BBs may hurt less esp in CQB conditions is because they have less inertia. Hence they would be decelerated by clothing more then a heavier BB which would have more inertia. There are other factors (gas behavior under compression, pressure and force, etc etc etc...) but the ones I have mentioned should be the major ones.

Last edited by Azuki; November 3rd, 2008 at 22:46..
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Old November 3rd, 2008, 22:40   #6
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Quote:
Originally Posted by mcguyver View Post
Heavier BB = more kinetic energy. Same as a real bullet.

And not all guns are consistant with delivering the same energy to BBs of different weights.

Case in point, my old KSC USP Compact. It shot 300 fps whether I used .20g or .25g BBs.
Correct and incorrect. An AEG's FPS is directly related to BB weight. Gas guns are not affected as much and retain higher FPS when shooting with heavier weights.
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Old November 3rd, 2008, 22:48   #7
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Quote:
Originally Posted by Styrak View Post
Correct and incorrect. An AEG's FPS is directly related to BB weight. Gas guns are not affected as much and retain higher FPS when shooting with heavier weights.
Sorry, there is nothing incorrect in what I said.

Explain please why my M16A3 PTW will shoot 0.25g BB at 497 fps but will shoot a .20g at 530 fps? 20% decrease in BB mass but only a 6.6% increase in velocity? Don't worry, I already know the answer.

My old Marui G3 shot 265 with 0.25g and 295 with .20g. Same BBs (I haven't changed brands in years). Same 20% decrease in mass, but now an 11% increase in velocity.

Not all guns are consistant, and you can't say across the board that an X change in weight = a set velocity change.
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Old November 3rd, 2008, 22:54   #8
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Quote:
Originally Posted by mcguyver View Post
Sorry, there is nothing incorrect in what I said.

Explain please why my M16A3 PTW will shoot 0.25g BB at 497 fps but will shoot a .20g at 530 fps? 20% decrease in BB mass but only a 6.6% increase in velocity? Don't worry, I already know the answer.

My old Marui G3 shot 265 with 0.25g and 295 with .20g. Same BBs (I haven't changed brands in years). Same 20% decrease in mass, but now an 11% increase in velocity.

Not all guns are consistant, and you can't say across the board that an X change in weight = a set velocity change.
Different barrel lengths and how your hopup contacts the BB also affect it. If you have a gun with the same barrel and same length and same/similar hopup you'll get most likely get very close to the same results. 30 FPS going from .20 to .25 seems right. That's what I got with my AUG with stock TM barrel. Notice both your guns changed by 30 FPS.

Also, BB mass % won't = velocity %.

And gas guns are a whole different deal too.
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Last edited by Styrak; November 3rd, 2008 at 23:00..
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Old November 3rd, 2008, 22:56   #9
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Load two different bbs and shoot yourself.
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Old November 3rd, 2008, 22:59   #10
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IMHO from experience a heavier bb will hurt more as in the end there is more weight in the object there for more force being distributed. Load a .20 and then a .28 and shoot yourself in each foot and see how the difference is.. I.E case in point when shooting through grass the .20's will fucking go everywhere as where the .28's bust right through and chop that shit up like a kick ass lawnmower..
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Old November 3rd, 2008, 23:00   #11
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http://img205.imageshack.us/img205/3...versionxq1.jpg

in reference to this quote - backing it up.

Quote:
Originally Posted by Azuki View Post
Kinetic Energy = 1/2 x Mass x Velocity^2

Simplified Kinetic Energy is proportional to the Product of Mass and the Square of the Velocity. So if you have a faster firing gun, the reason it hurts more when you use the same ammo is because there is more kinetic energy, just like you said.

When you fire an airsoft gun, the energy stored when the spring is compressed, in converted into energy carried by the BB. The spring will always transfer the same amount of energy to a BB, so according to the equation above an increase of mass result in a reduction of velocity. Conversely a reduction of mass for an equal amount of energy will result in an increase in velocity. The overall energy of the BB is always the same.

There are two things that affect how much the BB will hurt. First is the amount of energy the BB carries, and the second is impulse. Impulse simply is the amount of force applied over time. A high impulse (lots of energy over less time) tends to "hurt" more, while a low impulse (less energy over lots of time) "hurts" less. To visualize this, immagine a rubber ball, and a steel ball, both the same mass. A rubber ball imparts a lower impulse (less force per unit time) and a steel ball imparts higher impulse (more force per unit time) which is why you'd rather be hit by a rubber ball then a steel ball.

The difference in impulse between different BB weights is negligible if not non-existant since they are made of the same material more or less. Hence the amount a BB will hurt is only based on how much energy the BB is carrying WHEN IT HITS YOU.

This is where BB weights matter. A heavier (or technically speaking a more massive) BB has greater inertia. A lighter projectile will have less intertia and the force of friction/wind will affect it much more. A heavier projetile will have more intertia, and will not be as affected.

Therefore at point blank, both a 0.2g and 0.3g BB should "hurt" just the same. However at a longer distance, a 0.3g BB will maintain its velocity, and hence will hurt more.

I hope this helps you understand why it would hurt more or less .

EDIT: Also, the reason why lighter BBs may hurt less esp in CQB conditions is because they have less inertia. Hence they would be decelerated by clothing more then a heavier BB which would have more inertia. There are other factors (gas behavior under compression, pressure and force, etc etc etc...) but the ones I have mentioned should be the major ones.
Everything here is total truth.
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Old November 3rd, 2008, 23:02   #12
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Quote:
Originally Posted by Styrak View Post
[G]as guns are a whole different deal too.
That's certainly true - for AEGs you have a set spring and a set volume, etc. It always pushes the same amount of air at the same pressure when it fires.

GBBs on the other hand have the gas port of the magazine open for as long as it takes for the BB to exit the barrel. (At which point the chamber pressure drops, the shuttle valve flips, and the gas is then 100% directed to slide blowback, at the end of which closes the gas valve.)

How this affects the BB, I haven't been able to test since I haven't had enough gas guns and a chrono together at the same time to do it. I'd love to compare with an NBB (which I think should "act" more like an AEG's spring/cylinder setup.)

Last edited by DonP; November 3rd, 2008 at 23:06..
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Old November 3rd, 2008, 23:03   #13
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Quote:
Originally Posted by Styrak View Post
Different barrel lengths and how your hopup contacts the BB also affect it. If you have a gun with the same barrel and same length and same/similar hopup you'll get most likely get very close to the same results. 30 FPS going from .20 to .25 seems right. That's what I got with my AUG with stock TM barrel. Notice both your guns changed by 30 FPS.

Also, BB mass % won't = velocity %.

And gas guns are a whole different deal too.
Yes, I know. So why then do velocity changes drift so wildly for so many different guns? You answered the question already, and it boils down to my original point that not all guns are consistant. I was correct and you just reiterated that.

I go to my CQB PTW with the exact same cylinder, identical hop-up and the velocity increases about 8%.

So, unless you can build a formula that takes into account every length of barrel with every type of chamber with every type of hop-up rubber with every weight of BB, then my point still stands.
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Old November 3rd, 2008, 23:08   #14
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Quote:
Originally Posted by DonP View Post
Well, that's true - for AEGs you have a set spring and a set volume, etc. It always pushes the same amount of air at the same pressure when it fires.
Well, not always. The piston head o-ring takes time to expand, and the lube in the cylinder will play a huge part in how fast this happens. This is not constant over time (as effective lubrication is reduced over time) and susceptable to temperature as well. The faster that o-ring expands, the more air volume is available behind the BB.

Ever notice how a poorly lubed cylinder can have huge deviations in velocity? I've seen 30-50 fps in lots of cases, or how re-lubing (and changing nothing else) will bring velocities up and keep them consistant. This was an easy issue to see in the PTW, as you used to need to perform periodic, specific cylinder maintenance which included a cylinder re-lube.
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Old November 3rd, 2008, 23:13   #15
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Thats really cool. Where do you find stuff like that?
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