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VARIABLE

Velocity vs. Distance

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I want to know what the accuracy variences (per gun model manufacturer)are between semi/full auto?

 

i believe that its exactly the same between full auto and semi, although i may be wrong.

my reasoning is that its exactly the same circumstances, it just happens over and over again when in full auto. feel free to correct me on that though :D

 

one thing for sure is that on GBB's, full auto is useless as the kick-back makes it impossible to hit anything! although as an experiment i did mount a vertical foregrip on the RIS rail on my Glock 18c and it was MUCH easier to control!

 

oh, and USMC grunt, that doesnt really help, does it ;)

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I do not believe that is true simply because I've seen accuracy results of replicas mounted so as to take away the effect of human error and recoil and full auto still is more inaccurate. I believe this has something to do with the fact that full auto does a different cycle than semi.

 

If I'm not mistaken a site renegade recon performed simlar tests with the factor being stock vs. upgraded rather than bb weights. Very interesting experiment here, however unlike many who read this I'm not all too suprised with the results.

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I have often heard discussions about how .25s "teh pwn" .20s. Looking at the numbers and from personal experience, I always walked away from those heated disucssions scratching my head. I have shot both and seen little to no difference. I usually shoot targets in the "sweet zone" of 3-45meters where my BBs arent in the air longer than .5 seconds. I DID notice an accuracy difference between .20s and .30s though. I have since been told it has something to do with .30s resisting windage better or something. I tend to think that might be right. I had no idea why. That is why I came into this thread looking for answers. While that mystery remains...well a mystery to me, I HAVE gotten a bunch of fantastic knowledge concerning these tiny pieces of plastic. I so appreciate the efforts of the chaps that contributed their considerable noggin power to chew through the figures and the tiny plastic BBs they used to figure this all out. Thanks you guys for all your efforts.

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.20 would arrive at the target that split second quicker

.25 will hit the target with slightly better accuracy

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I have often heard discussions about how .25s "teh pwn" .20s. Looking at the numbers and from personal experience, I always walked away from those heated disucssions scratching my head. I have shot both and seen little to no difference. I usually shoot targets in the "sweet zone" of 3-45meters where my BBs arent in the air longer than .5 seconds. I DID notice an accuracy difference between .20s and .30s though. I have since been told it has something to do with .30s resisting windage better or something. I tend to think that might be right. I had no idea why. That is why I came into this thread looking for answers. While that mystery remains...well a mystery to me, I HAVE gotten a bunch of fantastic knowledge concerning these tiny pieces of plastic. I so appreciate the efforts of the chaps that contributed their considerable noggin power to chew through the figures and the tiny plastic BBs they used to figure this all out. Thanks you guys for all your efforts.

Glad to hear that you're finding the data useful, CeruleanSentinel. I find a lot of the science interesting but I'm glad others are still finding practical use for all of the information out there.

 

One thing that I'd like to stress as that the information I've listed here is somewhat old. All of the updated data can be found on the main website for:

The Airsoft Trajectory Project

 

That's not to suggest that anything stated here is wrong, but rather that the ATP website goes into much greater detail. A lot of it is thick on the science, but there are sections that make for interesting lay reading, such as the closing remarks section wherein I discuss the data as it relates to such questions as: which are better: 0.20g or 0.25g BB's, how do 8mm BB's compare to their 6mm counterparts, are 300' shots really possible, etc. The section can be found here:

ATP: Closing Remarks

 

All of the data there came about from careful modeling calculations measured against very thorough testing (sending several thousand BB's through chronos at various ranges).

 

In the Closing Remarks section, I do compare 0.20g BB's and 0.25g BB's in terms of range and time-to-target. For all practical purposes, both BB's go nearly the same distance (unless the shooter tends to over-hop the BB's somewhat, in which case the 0.25g BB's go quite a bit further). Both BB's get to the target at about the same time up to a range of 100', thereafter the 0.20g BB takes longer to reach the target as it is moving slower. I do not go into detail about the accuracy of the two, but my observation is that, with stock rifles, I typically get slightly better medium- and long-range groupings with the 0.25g BB's.

 

The simplest advice I give people is that 0.25g BB's do outperform 0.20g BB's slighly in both range and accuracy, and should be used if they're affordable or if you fire in smaller batches such as while milsimming with low-cap mags. I use 0.20g BB's for CQB (since both BB's perform nearly the same at short range), and use 0.25g BB's for everything else. But that's still only an opinion, which is all anyone really has on the subject. Even with "proof" of performance -- as depicted and explained in the Closing Remarks section -- it is still a matter of user-preference as to whether or not it's worth spending the extra money on the heavier 0.25g BB's.

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I am interested in checking out the ATP page but all I get is an error saying I don't have permission. Tried firefox and IE and get the same thing.

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Sorry, it's been a while since I've checked the site. I've contacted the owner at cybersloth.org and there is a password setup for public access. (I know, it's not really public access if you need a password, but it's the best I could do until the owner makes it such that it no longer requires a password).

 

User Name: airsoft

Password: atproj

 

If you run into problems accessing the site, contact the sites owner at:

webmaster@cybersloth.org

 

Again, the site should be freely accessible (i.e., no password) sometime in the near future.

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It's important to realize that bb's have no memory of what kind of gun they've been fired from or what the initial muzzle velocity was.

 

Wow really, I thought my BB's had souls! Guess I was wrong!

lolz jk

Great job, never realized how much science was in airsoft!

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What value were you using for the co-efficient of drag?

 

Also, the BB drop column should be irrelavent since the way gravity acts on a 0.2 or 0.25 BB will be the same according to the flight time.

 

What I mean is that, for example, 0.1 secs after leaving the barrel a 0.2g BB should have dropped the same distance as a 0.25. The difference, of course, is that the 0.2g BB will have travelled further because it's lighter.

 

Your figures don't actually dispute this (I don't think) but because you've tabulated the results by distance it's difficult to see for sure.

 

Also, while we're at it, care to show the formula and figures you use to arrive at your results?

I ask cos the last guy who did this came up with similar figures which showed that 0.25s were vastly superior to 0.2s.

However, all his data was based on a theoretical 3 second flight time.

Which is, of course, bonkers.

When I do these sums I always get the same curves as you've shown on those graphs but, based on a 0.5 second flight time (sensible for airsoft) the advantage of using o.25s is always marginal IMO.

Although what you're saying is theoretically true, you have to keep in mind that what your saying only applies in conservative (ie ideal) systems. The force of air friction in this system is non-conservative. If you understand P=mv, where P=momentum, m=mass and v=velocity, you realize that higher mass bb's will be better able to resist air friction because they can maintain their momentum for a longer period of time. The more mass it has(even though it's velocity is slightly less than lower mass bb's) the more momentum it has to resist the force of air resistance (coefficient of drag) This means they will drop "less" because they don't slow down as fast thus appearing to drop faster. In a vacuum, you are correct.

My explanation probably sucked, but I hope you get the drift.

 

*Note, the fluid dynamics of a sphere are very different when different conditions are present. For example, when hop-up is turned off, the way fluid (air) flows around the bb is drastically different (far more erratic) then when it is turned on and this will require that different sets of drag coefficients to be applied. I really like this data though, because it demonstrates the differences between high and low mass bb's very effectively

 

GREAT JOB VARIABLE!!!

Keep it up.

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*snip*

 

*Note, the fluid dynamics of a sphere are very different when different conditions are present. For example, when hop-up is turned off, the way fluid (air) flows around the bb is drastically different (far more erratic) then when it is turned on and this will require that different sets of drag coefficients to be applied. I really like this data though, because it demonstrates the differences between high and low mass bb's very effectively

 

GREAT JOB VARIABLE!!!

Keep it up.

Excellent point regarding different drag coefficients for spinning vs. non-spinning BB's. In Section I-D-07: Drag Coefficient of the ATP, I go into some detail about how the program I used calculated CD on the fly based on the Reynolds Number and the spin rate. I was surprised to find that BB's encounter less drag when hop-up is applied.

 

If you're interested, the page also references some of the better studies regarding the aerodynamics of spheres. My graduate work was in a slightly different arae of physics; their work was very useful. Achenbach's work in particular is seen as a seminal work on the subject and has been duplicated many times.

 

Thanks for the kudos. The overall project was a lot of fun and a lot of work; I do hope that people spend some time looking at the greater project because it goes into more detail about many different types of BB masses and different muzzle velocities (and answers quite a few easy questions). The major drawback of the entire project, though, is that it requires the reader to understand charts (there are around 300 of them) and have at least a basic understanding of math and physics. While that last page in particular is useful in proving or refuting certain points in airsoft, just as Galileo had a heckuva time proving that the Sun revolves around the Earth, I've had a difficult time explaining to people that the laws of physics are immutable and make no exceptions for airsoft.

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I read earlier in the thread how many people make mistakes estimating their distances and will argue to the end that they made accurate 200' shots. MIG1 and I were just shooting some of my guns last year and though we didn't have a tape measure, we estimated a distance to be around two hundred feet. I know my pace average from a Land Nav course I taught when I was a marine and my step is 28 inches. I then proceeded to step out the distance and boy were we surprised to find that the distance was only ~150'. I take distance results with a huge grain of salt unless the actual distance was measured.

 

Now a question to you Variable. how nay rounds did you have to expend for ranges longer than 25' as chrony's tend to be very finicky about where the BB actually crosses it's measuring eyes. Did you actually shoot to get those longer ranged figures or were they then based on calculations?

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Sgtwiltan: I'm not Variable, but I've chronoed BB velocities from up to 10 meters distance. Even at 20 meters the sideways deviation of a standard AEG is around 50-100 mm, so even though not all shots necessarily register, quite a few do.

 

-Sale

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Forgive me if it has been done already (haven't had time to read all the data yet), but I would like to see your results when using mass (.20g) and FPS (25fps intervals) to determine energy (in joules) at a certain distance (25ft intervals).

Almost a reverse comparison of VII.B

 

I was only able to use theoretical data based off of someone elses information with no real method of verification. I would like to see how close (or far off) my results are.

 

Here's my results:

joules.gif

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gu5t, try it with heavier ammo. Think of throwing a sponge ball with half your strength, then throwing it with all your strength. Range won't improve too much, but if you use the same strength with a pool ball, it'd go much further. Air resistance thing.

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Wondered if you gentlemen had heard of a program called chairgun. Originally designed for use by air rifle users it allows you to simulate adjustemnts to some of the parameters you are talking about.

 

Chairgun

 

I'm actually a Chairgun user, but Chairgun doesn't have a hop parameter, and you need to know or find the BC of your ammo.

 

Very few people around these parts are up to calculating BCs. Hop adds a really horrific variable to the whole thing, too.

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I'm no physicist, but is the drag greater on bbs than real bullets because they are round? This question has plauged me for quite some time and I think I have found the correct place to ask it.

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That is a bit of a loaded question...drag is greater on real bullets because they're moving a lot faster than BBs. But a sphere's coefficient of drag is higher than just about any bullet I can think of, so BBs definately don't fly as well as bullets.

 

Cd for a sphere is usually around .65 or so, +/- .1. For a bullet, it obviously depends quite a bit on the shape and size of the bullet, but .3 is average and some varmint rounds get as low as .15.

 

And PUMPUK...the 1J rule is gone.

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