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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 4th, 2008, 16:50   #46
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Lol fuck it! I'll just shoot people with whatever weight BB's I have handy!!
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Old November 4th, 2008, 16:56   #47
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if you're pissed off bbs hurt more that's why I insult the enemy first usually
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Old November 4th, 2008, 17:14   #48
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Quote:
Originally Posted by Jimski View Post
in joules

0.2g@350=1138
0.2g@380=1340
0.2g@410=1561

0.3g@350=1707
0.3g@380=2011
0.3g@410=2342

So (unless my calculations are crappy crapola) if switching to 0.3 makes you lose roughly 30 fps, you will still gain from 300 to 500 joules at these speeds (including speed decrease), while a 30 fps increase at constant weight will only add 200 joules at 0.2g and 300 joules at 0.3g.

actually theres a slight calculation error in ur formula.
E=.5*m*s^2, where E is in joules, M is in KG, S is m/s
so a .2gram bb is .0002KGs, and at 100m/s = 330fps
E=.5* .0002 * 100*100
E=1 Joule
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Old November 4th, 2008, 17:23   #49
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yes I took g instead of kg, silly me, 2000 J BBs

but what it says makes sense nevertheless, going heavier will hurt/penetrate more than going faster.

personnaly I choose faster BBs for CQB and heavier BBs for long range.
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Old November 4th, 2008, 18:50   #50
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Best way to visuallise it.

Try hitting someone with a 45lbs weight in your hand. Slow, but devastating.
Now, hit the poor bastard with a 2lbs leather wip. Fast and paintfull.

So what?

The eavyer you hit, the more energy is transfered and the more damage is done. The lighter the hit, less damage.

We feel pain differently though. Both BBs will be painfull, but heavyer BBs are more prone to leave a mark on bare skin at equal velocities.

All that mess would be solved if we forget about fps and think only about joules.
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Old November 5th, 2008, 03:14   #51
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OK, a quick recap. The question I posed myself (and you fellows) was "All other things being equal, would loading lighter ammo into the same gun cause less of an ouch?"

A practical application of this would be loading a gun (like a sidearm) with .12g BBs in order to make it more CQB-friendly. Could this be reasonably expected to help?

It seems some people think yes (heavier ammo = more energy = more ouch), some people think no (lighter ammo = higher FPS = same energy), and some people like to argue.

Well, nothing gets the brain working like a good experiment.

Disclaimer: I did specifically lay out that this was half-assed science time.

My hypothesis: Lighter ammo will overall transfer less energy, compared to heavier ammo from the same gun.

The test setup: Putty is used as a way to capture and visualize BB energy transferred. Shoot the putty from point-blank ranges with a variety of BB weights (.12g, .20g, .28g, .30g) from a variety of guns. Measure the results with a depth gauge, and eyeball the hole.

Why do it this way:
Three main reasons:
  • The putty deforms when hit, and "freezes" when no more energy is spent deforming it. This is easy to measure and seems to be a consistent measure of energy transferred. As a side note, energy transfer should be optimal since the BB stays in full contact with the putty until it is no longer penetrating (energy transfer being a function of how long something can stay in contact over how much area, and all that. No glancing shots, etc.)
  • It therefore doesn't matter that putty doesn't act like skin, or that skin in different spots feels pain differently. We're interested only in relative energy between different weight BBs from the same gun. As long as it's consistently measured, we're good.
  • Shooting things that do something when you shoot them is fun.

Assumptions, Out Of Scope, etc:
  • In all individual tests: Same gun, same propellant, same putty, same range.
  • We are not measuring quantative energy, just relative energy between different weight BBs from the same gun. So converting "size of dent" into "joules" or whatever isn't in scope.
  • The bigger/deeper the hole in putty, the harder the hit.
  • The harder the hit, the bigger the OUCH potential.
  • Only point-blank ranges are tested. Results valid at point-blank will be valid at longer ranges since it's impossible for a BB to go faster the further it goes.
  • In other words, if a .12g BB doesn't hit as hard as .20g at point-blank, it never will no matter what range you go out to.
  • How well energy is retained at longer ranges for different weights is out of scope. (Meaning whether .20g retains energy better at longer ranges than .12g is out of scope.)

TEST RESULTS

This is a typical target:


First up is a KJW 1911 Gas Blowback on duster at point-blank range (2m). NOTE THAT THE WHITE SPOTS INSIDE THE HOLES ARE PAPER FRAGMENTS. BBs DID NOT PENETRATE.

Observations: There is a clear progression in penetration depth related to BB weight.

Next is the same KJW 1911 Gas Blowback, but this time with a CO2 magazine.

Observations: The relation of penetration to BB weight is still clear. Overall all BBs penetrated further. The CO2 mag was observed to shoot noticeably harder.

Next up is a KJW MK1 Non-blowback on duster.
The non-blowback should fire the BB with a fixed "gas charge" unlike a GBB which keeps the gas on as long as the BB is in the barrel. This surely has some kind of effect on BB fps, but that's not specifically of interest here -- does a NBB versus a GBB change the trend we're observing?

Observations: Same progression observed -- more BB mass means more observed putty penetration.

Finally we have an APS2 bolt-action spring rifle.


Test 1 Observations: All BBs except for .12g penetrated into the backstop. Clearly .12g had less energy, but what about the rest?

Another test was done, this time with BDU material in front of the putty instead of a paper target.


Observations: Same trend observed as all previous tests. Heavier weight from same gun = more penetration.

A NOTE ABOUT MEASUREMENTS
Two decimal places of measurement for a depth gauge into putty smacks of "measure with micrometer, mark with chalk, cut with axe." This is not lost on me. So I did a quick test where I shot the putty with 4 rounds of .20g and measured each. The measurements were remarkably consistent; biggest deviation was .12mm. Admittedly it's a small sample size (just like the rest of this experiment) but it looks like putty is not only consistent but the depth gauge is as well. At least, enough to see what I'm trying to see.


CONCLUSIONS
  • Heavier BBs (i.e. more mass) fired from the same gun equals more energy transfer on impact. (Compared to lighter ammo)
  • Lighter BBs (i.e. less mass) fired from the same gun equals less energy transfer on impact. (Compared to heavier ammo)
  • The different mechanics of operation between a NBB versus a GBB versus a spring piston doesn't change this.
  • Shooting stuff is pretty fun.

Therefore, while pain is subjective and depends on where and how one is shot, I think it would be reasonable to explore loading .12g BBs into a gun for the purposes of making it more appropriate for CQB - for example into a gas gun sidearm which otherwise might shoot pretty hot. (And CQB is an environment where the poor accuracy of .12g at range won't be much of an issue.)

Whether it actually makes enough of a practical difference to make a hot gun safer? Maybe!

Last edited by DonP; November 5th, 2008 at 03:51..
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Old November 5th, 2008, 03:17   #52
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^^ nice post lots of good info . this should be sticky
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Old November 5th, 2008, 03:21   #53
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Nice work DonP!

I do have some concerns with your use of putty as a target media though:

-varying thickness in putty target
-many putties are non Newtonian

It seems that your putty pad isn't very thick. Thin pads bring the backstop into play when the putty deforms and backs into the rigid backstop. I would think that a very thick pad of putty (say 2") would reduce the effect of varying thickness to the backstop by taking the backstop out of the deformation behavior altogether.

Most putties tend to be non Newtonian. Their apparent stiffness is highly deformation rate dependent. Faster deformations may absorb more energy than slower ones which directly affects the damage potential we wish to observe.

I think it is also important to also measure the muzzle velocity just before the pellet impact. Making an assumption of constant energy may be a mistake when you're trying to correlate performance with damage potential.

2m is not exactly point blank in airsoft terms. IRC my shots at my Prochrono indicated up to 20fps velocity loss with high energy rifles shooting 0.2g pellets at 10'. Heavier pellets exhibited lower velocity loss. I think you need to blast your targets at 6" instead of 2m (~7')
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Old November 5th, 2008, 03:38   #54
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Quote:
Originally Posted by MadMax View Post
-varying thickness in putty target
Hmm, that's true. While my putty thickness was pretty even (used a roller and measured the first few, I didn't measure each and every one.

It's possible --- unlikely I think (but of course I would think that since it would go against my hypothesis) but possible that some of the BB impact areas were markedly thicker than others. But so much that it would throw off the observed trend? Maybe.

Quote:
It seems that your putty pad isn't very thick. Thin pads bring the backstop into play when the putty deforms and backs into the rigid backstop. I would think that a very thick pad of putty (say 2") would reduce the effect of varying thickness to the backstop by taking the backstop out of the deformation behavior altogether.
I did notice some BBs hits deforming the back of the putty pad (see the APS2 result for the .12g - it deformed the back even though it actually didn't penetrate that far.) This does affect the "toughness" of the putty, but I figured that the effect should be consistent across all the BB hits, and should all cancel out, no? Again, I'm probably just happily declaring immaterial something that would otherwise require me to set the test back up and challenge my assumptions. Screw that.

Quote:
Most putties tend to be non Newtonian.
Hmm, this is a really good point I hadn't considered. Maybe ballistic gelatin would be better. But much messier and harder to set up, so therefore surely it wouldn't be worth trying!

Quote:
I think it is also important to also measure the muzzle velocity just before the pellet impact. Making an assumption of constant energy may be a mistake when you're trying to correlate performance with damage potential.
Do you mean measure the muzzle velocity between different shots of the same BB weight to make sure I'm not getting the odd "hot shot" or something?

I don't see velocity being relevant otherwise, unless I'm missing your meaning.

EDIT: Oh, I think I get it. Repeating the tests at 6" might be interesting just to see if (and how much) .12g penetrates more at 6" as opposed to 2m. If there is a condition where lighter ammo possibly gets MORE penetration, I guess it would be right at the muzzle or never.

Last edited by DonP; November 5th, 2008 at 03:52..
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Old November 5th, 2008, 03:59   #55
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I'm guessing that the putty behaves incompressibly when it deforms so some sort of flow has to occur to create a bb crater. Given the flow-velocity issues I would think that it would be best to take the backstop out of the behavior and have the putty flow uninfluenced by a rigid backstop which imposes some funny shear behavior right at it's face. I would think that this factor would exacerbate the non Newtonian behavior of the putty.

I've been guessing that equivalent energy for different weight pellets would have the same potential for doing work when they smash into things. I suppose the only other absorption for energy (other than deformation) could be heat which could be significant for viscous media like putty which does transform a fair bit of work into heat when you knead it. I don't know how the heat issue translates into pain factor, but it's hard to measure the temperature rise in the immediate impact area and this would be unaccounted energy.

I've found AEGs to be largely constant energy devices, but when shooting very low weight pellets this behavior starts to break a bit (IRC it's been a really really long time since I did this battery of tests). I suspect that very light pellets offer such a low resistance to flow that other restrictions and the piston mass start to eat up more energy. This is why I suggest measuring impact fps. Also it does help to throw out the odd hot shot.

Now that I think of it, quantifying damage potential is a very difficult problem. The influence of speed and penetration are pretty well documented. At some point very very fast projectiles cause cavitation and end up destroying themselves in most ballistic media while slower heavier masses can achieve much deeper penetration. Our dinky balls operate in a completely different velocity regime, but I think it's hard to determine an accurate correlation between penetration and pain without using a media which actually simulates human flesh. I'm starting to come to a better appreciation of why the FBI chose ballistic gelatin because it offers a good analogue to tissue to assess penetrating damage.

In our very low energy situation with light projectiles, I think we need to choose a medium which is significantly less dense than our projectiles. It's obvious that dense media will significantly slow faster less dense projectiles with flow resistance, but I argue that this is not a good indication for low pain since our projectiles usually don't enter into the body and experience surface flow resistance.

I'm thinking we need a hybrid target that behaves in a Newtonian manner with an unpenetrated skin (like your cloth outer). Maybe a foam target that isn't resiliant with a cloth outer might be a good target. It would exhibit low rate dependent behavior and still provide a permanent deformation to assess. Maybe put a canvas cloth on that green sponge that flowers get stuck into.
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Old November 5th, 2008, 04:32   #56
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Quote:
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Why not just get a chrony that can rate joules... and fire through it with the same gun at different distances with .2 and .3?

see which one retains more energy
Sorry, read that and just brought back memories of chronies with shattered LCD screens, made me laugh.

One guy I know says .28's can be easily dodged and .25's can't because of the fps difference, so to test it I got him to try to dodge .28's out of my M14 and .25's out of an M4. He started babbling some equations and physics at me (hes an engineer) and then I broke it to him that the M14 is shooting .28's faster than the M4 is shooting .25's (the M14 is semi only.)

All I know is with .28's you can't use foliage as hard cover very reliably but with .25's out of the same gun the leaves and branches stop the BB's in their tracks. Heavier BB's are also more accurate, and only wimps complain about weight differences causing extra hurt.
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Old November 5th, 2008, 04:46   #57
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Very nice analysis. There's only one problem with it. You're using gas guns in which the FPS is affected less than an AEG. ex) Using heavier BB's does not translate to the same drop in fps as AEG's.
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Old November 5th, 2008, 08:55   #58
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Quote:
Originally Posted by Styrak View Post
Very nice analysis. There's only one problem with it. You're using gas guns in which the FPS is affected less than an AEG. ex) Using heavier BB's does not translate to the same drop in fps as AEG's.

Barrel length factors in for AEGs. A short barrel AEG will behave that way, too.

Also, Don's original reason for posing the question was with respect to using GBBs in CQB/close range, and the safety claims that go along with that (and if using lighter ammo would be safer).

And there was an APS in there.

@Don: you could make some airsoft-caliber ballistics gel with some kitchen grade gelatin
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Old November 5th, 2008, 09:52   #59
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We used to use plumbers putty as a back stop for pellet shooting. When we once did "testing" (really just goofing around), we used two sticks of equal thickness and a rolling pin to achieve a consistent thickness for the test medium. Same way that you grade gravel for interlocking brick.

We did find that you needed "extra" medium so that there would be enough give in the medium, otherwise an adjacent shot would tend to deform things too much. Maybe not a problem with yours as essentially a backer was used. (we used 2" thick free standing chunks)

It would be most interesting to repeat these test at a further distance to demonstrate the momentum effect of heavier bbs. 2m vs. length of basement.

Nice stuff!

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Old November 5th, 2008, 10:57   #60
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It's simple, heavy BBs concerve their energy longer. They need longer MED to be safe at hight fps, like for snipers.

I like your putty test DonP. Even if it's not scientific, it's still a good example of what happend.

Now trie this. With the same gun, fire a .25g BB at 350fps at 10fts of your target.

From the same gun, load .20g but get closer.

See at what distance, the .20g BB will have the same impact penetration as the .25g BB.

At 350fps, a .25g BB will have about a 1j impact at 10 fts. That would be the MED for this velocity and weight.

To validate the MED thing, if you can try a 450fps rifle, shooting .30g at 40fts of the target, you should also see similar penetration as the .25g, since it take 40fts for a .30g at 1.88j (450fps) to attain 1j of energy. That's it's MED.

All fps values are mesured with .20g.
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