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Time to share........... Airsoft Ballistics



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Old February 24th, 2007, 15:47   #1
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Time to share........... Airsoft Ballistics

Since I just posted it for general info on the Ottawa Valley Airsoft forum (it originated on the Warmonger's forum under my personal Sniper's Range section) I just added a few more paragraphs to the end of it, figured I'd share with all. Critique it if you like, might help me understand the entire thing better myself, and I can further inform others via changes I make and/or tests I attempt.

Originally Posted by Stalker
Here's an info thread I composed last year on my team's forum ( )under my 'Sniper's Range' section. It primarily is written to inform others about my airsoft experiences and my constant study of airsoft ballistics regarding being an airsoft sniper. But a lot of it is still very applicable to AEGs, etc.

Enjoy, and let me know what you think, if it helps you understand better, etc.

Ok, here I'm going to attempt to outline airsoft ballistics (as it applies to sniper rifles) as I have experienced it and as I understand it. It seems that the general concensus is that it's all in the fps, which isn't completely true. Well, paritally it is, but it's not a "Be all, end all" solution. I'm going to break it down into the three basic areas: Velocity, hop up, and BB type and choice. And I am placing it in this section because it's more important for a sniper rifle since you aren't dumping a lot of plastic downrange.


Ok, this IS an issue and will help dictate the range the BB will travel. Consider it to be 2/3 of the entire determination of range & accuracy. A BB will go straight out to a certain point that it'll get to the ratio of speed vs. BB weight vs. hop up backspin.

The velocity determines how far the BB will go before that ratio is acheived. The higher the velocity, the farther the BB will go before it goes up or down (or in the case of side wind, how far it goes before it blows off course.)

Keep in mind though, that velocity doesn't play such a huge role that one can't get long range unless the gun is really hot. Remember I hit a guy 200ft away at Op: Cold Wind? My M24 at the time was shooting around 400fps. Last I chronied at the LZ, it shot a .36g BB at 315fps with full hop up.

Hop up

Here this is, we all know how it works. It takes over the rest of the distance after the velocity gets to that magic point and carries the BB farther.

BB choice

This is the tough one as it's based completely upon the gun and hop up. You adjust the hop up based upon the weight. (NOTE: The APS2-SV has a fixed hop up set for Maruzen .29g SGM. Means that .36g will be too haevy, therefore .30g is best overall use. Unless you are shooting really high, upwards of 500fps with .2g BBs, then you might find even the .36g BBs are over hopped, in which case you shift over to .43g BBs and live happily ever after.)

Seems that the higher the fps, the more erratic the hop up and accuracy is. When my M24 was shooting around 500fps (when I first got it), I could barely get a .36g BB accurately out past 150ft. Yet with full hop up and shooting 400fps, I could easily get it past 200ft.

The higher the velocity, the harder it hits the hop up, the faster the back spin on that BB (we'll say RPM for the fun of it, since that's essentially what it is), which means that aerodynamically, it will be much more unstable and therefore inconsistant. Remember that there are various uncontrollable air currents at every point between you and the target. Any irregularity in the air will send the BB with a fast backspin off course, where a slower spin will be more stable through those air currents.

The weight is obvious to us all as well. The higher the fps, the faster a heavier BB will go, etc. Heavier is needed to punch through leaves and crap, as well as making it less suseptable to wind and air movement. Added bonus is that it hits a lot harder than a lighter BB, and if you shoot a guy with a single BB, you want to make sure he feels it to call himself out (really sucks to get an obvious hit on a guy only to see him react then decide to ignore it and keep playing.) So we need as heavy as we can get to work well with the gun. Lighter BBs out of my M24 aren't that shit hot, .36g seems to be the best, .43g seem too heavy for the level of hop up I can get out of my M24. Same as .36g BBs are too heavy to use in the M700 (not enough hop up to get them past 150ft, even with propane). I recommend .30g BBs for the M700, adjust hop up to suit.

BB brand choice is another issue all together. Believe it or not, the Straight graphite .36g BBs are considered in the airsoft sniper circles to be very inconsistant and basically crap (but the WHITE .36g are considered better). Surface irregularities (as well as the inside of them, yet the .43g BBs are considered to be better due to the denser composition inside) cause them to fly when you don't want them at times. Out of a mag of 10, you might have one or two that go screwy, maybe 3 to 4. Maybe none! No way to tell. Also the issue is within the BB. Most BBs have an airbubble inside from manufacturing. The better brands have this pretty close to center, the cheaper ones don't, which makes them fly like a paintball which the paint has settled on one side. Best for airsoft are the Airsoft Elites, but not so good for sniper rifles due to the light wieght. Best for sniper rifles are the Maruzen Super Grandmaster .29g BBs (obviously, $15USD for a box of 500).

Hope this helps you guys understand the issues to consider when it comes ot sniper rifles. Higher velocity isn't always a good thing, and very hot guns will burn us for limits, yet might not nearly be as consistant or accurate as a lower fps will. I know guys in the states that can get a .29g SGM BB (guns shooting 500-550fps with .2g) out to 300ft and 6-7 times out of 10 hit a reasonably sized tree. But that's only in low wind conditions. If I was able to hit a 12" tree at 230ft away with .36g BBs flying at 315fps.................

Oh, last to write. The higher you make your gun shoot, in the case of bolt actions, the faster it'll wear out, in my case not cutting down my 300% spring will make the bolt pull much harder, high chance of ripping my bolt handle off, and the heavier the trigger pull will be.


Posting new stuff.


Temperature affects real steel bullets, especially at longer ranges, and it'll affect airsoft just as much, if not more. Colder air is more dense than warmer air, so in colder weather the hop up effect will be more exagerated (hop up creates lift, lift is dictated by the density of the air under the BB) and in warmer weather the same setting will have a lesser effect. Make sure to adjust your hop up before every single game, it's not just about setting for different BB weights, it's also to compensate for temperature.


We all know wind is a pain in the ass as far as airsoft goes, especially with our lightweight BBs. Having yoru hop up set for say, 0.25g BBs in still conditions, once you intoduce wind with the same setting you'll find your hop up gets more exagerated. Wind is a higher density of moving air. See above about lift vs. air density. The main difference between wind and temperature, is temp remains pretty constant around any areas you will be playing, but wind will be completely variable, as well as wind having direction. Shoot with the wind, hop up effect won't change very much. Shoot into the wind, you will easily overhop. Add in shooting perpendicular to the wind, same effect as into the wind, but your BB will carry more to one side or the other. Best case for actually playing is to set your hop up a touch under flat & level setting. It's FAR easier to raise your crosshairs a slight bit to get your BB on target, than it is to lower your crosshairs because your gun is overhopping and try to hit your target.


An odd one that most of us tend not to experience, but is worth mentioning. Shooting downhill at an angle your BBs will overhop by roughly a foot or so due to gravity not being perfectly perpendicular to your shot. Opposite effect for shooting uphill. Keep that in mind if you are ever looking down at someone from a hill and planning to send them to re-spawn.

Difference being in all the above, an aimed chest shot could very well nail your target in the mouth or face. Happened to me once when I tried using 0.25g BBs in my M24, aimed at Shaddy's chest about 80ft away (my M24 was shooting about 380fps at that point in time) and the wind was at his back, he was walking towards me. I shot, something on the ground made him look down, my BB went severely upward about 6ft away from him, slammed into his lower lip. It bled and swelled pretty bad. He was cool about it then and even now, but I learned a lesson about shooting into the wind. ops:

Last edited by CDN_Stalker; February 24th, 2007 at 15:54..
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Old February 24th, 2007, 15:53   #2
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Old February 24th, 2007, 15:55   #3
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Here's another good one:
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Old February 24th, 2007, 15:57   #4
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Originally Posted by The Saint View Post
Nice!! I'll give it a read later, scanned over it, parts of it are well done, will post it here for eternity sake!

Oops! I'd forgotten to update the sections regarding Kinetic Energy, Crosswind Component, Temperature, & Altitude. I've updated each section with the correct text & graphics. Thanks to the folks who pointed it out via email!


I’m always trying to figure out the science behind the sport. Whether it's golf, football, tennis, or airsoft, I like to get into the details of what happens in terms of physics. Taking this approach to airsoft, I decided to set out to estimate trajectories based on experiments and the myriad equations for calculating trajectory. In the end, I had compiled the equations necessary to calculate the many forces acting upon airsoft BB's, coupled that with a little know-how and developed a program in MATLAB to ultimately calculate projectile trajectory. Basically, the program can be used for paintball, regular 0.177 BB’s, as well as airsoft BB's. It is designed to account for:

- muzzle velocity

- mass of projectile

- diameter of projectile

- altitude

- temperature

- air density / pressure

- wind and wind direction

- crosswind component

- amount of hop-up applied

The gun the BB is fired from is irrelevant. Once the BB leaves the barrel, it has no memory of the gun it was fired from. It has a magnitude (several, technically) and a vector, and in terms of physics, that's all that matters. Consequently, I needed to model the data knowing the initial velocity of the BB, the direction of the BB, and the spin that the BB incurs from hop-up. Granted, different guns will have a slightly different directional component when the BB exits the barrel (and we're talking VERY SLIGHT), and hop-up varies from unit to unit, however the program assumes that the BB is following the path dictated by the direction of the barrel, that the muzzle velocity is, at worst, +/- 2% of it's average muzzle velocity, and that the hop-up is capable of putting a consistent amount of backspin on the BB (i.e., it has been "broken in").

Before publishing calculated results, I went to great lengths to make sure that the calculations were accurate in terms of describing the actual trajectory. I spent several months performing tests, gathering data, contacting other scientists in the know, reading a plethora of theses, collecting information from others who had collected data, staying up late at night jotting down equations (and scratching through yet more equations), testing algorithms, performing tests AGAIN to ensure that I hadn't made errors in my methods, and of course many hours of the standard vitriolic spewing that occurs when you just can't get the programs to work.

Ultimately, all of the testing verified the final calculations. For more information on testing methods and validation, consult Section II: Testing and Model Validation.

Having verified the data, the next thing I wanted to do was calculate standard trajectory, hop-up trajectory, energy dissipation, velocity reduction, time of flight, minimum engagement distances, and the effects of altitude and temperature for a wide variety of muzzle velocities and BB weights and post the results online. Hopefully it will answer many of the questions people are putting forth about airsoft rifles, questions such as:

- What is the terminal velocity of a 0.20g BB?

- Is it worth upgrading a gun from x fps to y fps to get more range?

- For equal muzzle energies, which BB goes further, 0.20g or 0.25g?

- Which mass BB gets to the target the quickest for the given velocity?

- Do heavier mass BB's have more energy than lighter one down range?

- Is it necessary to restrict a rifle with a 600 fps muzzle velocity to a minimum engagement

distance of 100 feet?

- What MED's are recommended to ensure both safety and fairness to all shooters?

- Will lower temperatures increase or decrease range?

- Does altitude really affect trajectory and minimum engagement distances?

- Do 0.43 gram BB's negate the effects of wind that much better than 0.20 gram BB's?

- Do 8mm BB's resist the effects wind better than 6mm BB's?

- Do high-velocity BB's resist wind better than low-velocity BB's?

- What's the effective range on my rifle?

- What's the absolute maximum range on my rifle?

- Are people really able to achieve ranges out to 300 feet?

- Do 8mm BB's provide better range than 6mm BB's?

Those are all good questions. Unfortunately, I've seen many answers out there that are, at best, just guesses. And more often than not, I've seen answers that simply disagree with the laws of physics. Hopefully all of the data will provide people with some answers to these and other questions. If you find yourself in disbelief over what the calculations depict, spend some time looking at the equations; they're the standard equations used for this sort of thing and are universal when it comes to ballistics. Even if you're still not convinced, spend some additional time reading about the methodology used to verify the equations. If you're not convinced after that, I encourage you to do some testing and see how your results compare.

Additionally, I realize that airsoft is an inexact science. Air pockets, surface bumps, diameter inconsistencies, shifting winds, muzzle velocities inconsistencies... these things and others lead to erratic behavior in a BB's trajectory down range. Even so, I think that it is better to have a rough idea of what the "ideal BB" would do in flight, and allow the shooter to factor in their own "fudge factor."

In terms of usefulness, those using upgraded guns or guns that tend to have a high degree of accuracy will benefit most from the data. If your gun's muzzle velocity varies by 20-30 fps per shot or if, for a variety of reasons, your gun is incapable of reproducing the same trajectory shot after shot (and frankly some of mine fit that description) then the data may be less useful. Ultimately the usefulness of the data will be determined by the end user and will still be dependent upon how familiar the user is with their gun. For me, I think that it is very handy to have. But of course, I am biased.

Anyway, here are the data. It's divided up into many sections as it's all a little overwhelming (with around 270 charts and graphs). It's designed to be read from start to finish so if you can't figure out something in a later section, chances are that the explanation was provided in an earlier section. (And, if you're still trying to make sense of all of the questions above, they're answered concisely in Section IX: Closing Remarks.)

If you have a question or comments about the data, or would like to see some additional analysis or data plots, feel free to contact me. Particularly if you want advice or graphics depicting recommended Minimum Engagement Distances, drop me a line and I'll try to help make some tailor-made plots for use at your airsoft site.

Lastly, while I consider the hop-up trajectories to be close, they're not perfect; if you have an opinion or have observational information concerning trajectory, by all means drop me a line. Doing so will help to modify some of the coefficients that affect hop-up calculations. I hope to eventually post a program online for people to download so that they can calculate trajectory for their own rifles, however given the lack of copious spare time, it may be another year or so before I can develop the online calculator.


December, 2006

I. Physics Principles and Equations

A. Physical Characteristics of BB's

1. Diameter

2. Volume / Density and Terminal Velocity

B. Air Density

C. Kinetic Energy

D. Forces Governing Trajectory

1. Drag Force

2. Velocity

3. Distance

4. Magnus Force

5. Terminal Velocity
6. Spin Decay
7. Drag Coefficient
8. Lift Coefficient
9. Gravity

II. Testing and Model Validation

A. Verifying Velocity Calculations

III. Effects of Hop-Up

IV. Effective and Maximum Range for 6mm BB's - Still ironing out "effective range..."

V. Environmental Effects

A. Effect of Wind on Trajectory

1. Headwind / Tailwind Component

2. Crosswind Component

B. Effect of Altitude on Trajectory

C. Effect of Temperature on Trajectory

VI. Minimum Engagement Distance

A. Determining Muzzle Energy
B. Safe Impact Energy
C. Recommended Universal MED's
D. Tables for Determining Minimum Engagement Distances
1. MED's for 0.20g, 6mm BB's
2. MED's for 0.25g, 6mm BB's
3. MED's for 0.30g, 6mm BB's
4. MED's for 0.36g, 6mm BB's
5. MED's for 0.43g, 6mm BB's
6. MED's for 0.34g, 8mm BB's
7. MED's for 0.45g, 8mm BB's

VII. Tables for Energy Based on Muzzle Velocity

VIII. Modeled Data

A. Interpreting Plots

B. Velocity Comparisons Using BB's of Equal Masses

1. Velocity Comparison Using 0.20 Gram BB's

2. Velocity Comparison Using 0.25 Gram BB's

3. Velocity Comparison Using 0.30 Gram BB's

4. Velocity Comparison Using 0.36 Gram BB's

5. Velocity Comparison Using 0.43 Gram BB's

6. Velocity Comparison Using 0.34 Gram 8mm BB's

7. Velocity Comparison Using 0.45 Gram 8mm BB's

C. Mass Comparisons of Projectiles Fired at Equal Energies

1. Effects of Different BB Masses Fired at 0.37 Joules (200 fps Using 0.20g)

2. Effects of Different BB Masses Fired at 0.47 Joules (225 fps Using 0.20g)

3. Effects of Different BB Masses Fired at 0.58 Joules (250 fps Using 0.20g)

4. Effects of Different BB Masses Fired at 0.70 Joules (275 fps Using 0.20g)

5. Effects of Different BB Masses Fired at 0.84 Joules (300 fps Using 0.20g)

6. Effects of Different BB Masses Fired at 0.98 Joules (325 fps Using 0.20g)

7. Effects of Different BB Masses Fired at 1.14 Joules (350 fps Using 0.20g)

8. Effects of Different BB Masses Fired at 1.49 Joules (400 fps Using 0.20g)

9. Effects of Different BB Masses Fired at 1.88 Joules (450 fps Using 0.20g)

10. Effects of Different BB Masses Fired at 2.32 Joules (500 fps Using 0.20g)

11. Effects of Different BB Masses Fired at 2.81 Joules (550 fps Using 0.20g)

12. Effects of Different BB Masses Fired at 3.35 Joules (600 fps Using 0.20g)

D. Addendum

1. Velocity Comparison Using 0.28 Gram BB's
2. Velocity Comparison Using 0.29 Gram BB's
3. Velocity Comparison Using 0.88 Gram BB's

IX. Closing Remarks

X. Online Calculators

A. Online Calculator - pending

B. MilDot Scope Calculator
C. Relative Energy / Minimum Engagement Distance Calculator

IX. References -- pending

All text, images, and linked webpages are the property of and may not be reproduced without permission. For more information, contact

The Airsoft Trajectory Project

Copyright © 2005-2006 - All rights reserved

Hmm, I didn't take into account increased drag in colder weather. Have to rexamine and test a few things.

Anyways, while I didn't take the physics route with tables and such, the majority of the info here should help people understand better what to use and what to expect/counter.

Last edited by CDN_Stalker; February 24th, 2007 at 16:13..
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Old February 24th, 2007, 16:15   #5
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i hope this thread get stickied
Finished and installed my SL8 style stock.
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Old February 24th, 2007, 18:43   #6
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GREAT POST! Very well written and good work on laying it simply for those that might not get the science of it all.


P.S. Real question is - what's better, paintballers or airsofters? hah...
"It is better to be hated for something you do, then to be hated for something you don't do".

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Old August 11th, 2007, 13:55   #7
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this thread was very helpful...
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Old August 11th, 2007, 20:36   #8
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Originally Posted by DONSTER 125 View Post
this thread was very helpful...
Good, which is enough reason to bring it back (thanks).
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