Official ASC Bladesmith
Join Date: Jul 2003
Location: Ottawa, Ont.
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 ( http://warmongers.ca/
)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.
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.
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..