Firepower! Guide to Airsoft FPS [Test Your Limits]

Guide to Airsoft FPSPlayers, especially new ones, often are all about getting the gun that slings BBs at the highest Feet Per Second possible. However, all the FPS in the world won’t do you any good if your field won’t let you run your gun because it shoots too hot. There are a few factors in play that might decide how much your maximum firepower really is, which can make the difference between a great purchase and a terrible one.

What’s up with FPS?

The standard, at-a-glance measurement of how much gun one has in the airsoft world is pretty simple one – load your gun with some 0.20g BBs and see how fast they come flying out the end. As a general rule, guns used at close quarters battlefields in North America are limited to no more than 350FPS, although you might find some sites that allow for hotter shooting guns and some sites that require even less FPS. Meanwhile, at outdoor fields all across North America, guns are typically allowed to shoot 450, 500, or even 550 FPS. However, these high allowances for BB flight speed typically incur some sort of minimum engagement distance that increases the closer one’s gun is to the field’s maximum FPS limit.

gun shotWhen purchasing a gun, the first question that should cross your mind is “Am I intending to use this gun for CQB, outdoor fields, or both?” Figuring that out is all fine and dandy, but if you’re ordering from outside of your country, there’s another factor you might want to watch out for, lest you entirely waste your hard-earned money on a useless purchase – customs clearance. Depending on where you live, your country has certain laws in place as to what is and isn’t a controlled firearm. I’m a Canadian, so naturally, I have a rather silly set of limitation as to what Airsoft guns I can and cannot bring into my country.

In my case, the only acceptable airsoft guns for import are those which shoot between 366 FPS and 500 FPS. Any lower or higher and my airsoft gun becomes classified as a dangerous firearm with red tape and gun laws as far as the eye can see. This will likely result in the airsoft gun being destroyed at the border or returned to sender, wasting my money. Of course, once it’s actually in Canada our airsoft guns can shoot at any FPS so long as it BBs has less than 5.7 joules of force behind them, meaning they can legally be well above or below the import limitation, but that’s Canadian gun laws for you. They’re strange, but in this case, I’m not complaining! However, it goes to show that your legal import restrictions might differ from legal usage restrictions.

On that note, if you’ve ever wondered why Tokyo Marui guns tend to have a pretty low FPS rating compared to other guns on the market, country FPS limits are why – Tokyo Marui guns are meant for the Japanese market where guns are restricted to under 325 FPS.

Joules Though, What are Those?

Remember when I said FPS was the at-a-glance measurement of how much gun you’ve got? Well, airsoft is a competitive sport, and naturally, competitive players like to find ways to get an edge on one another. In terms of airsoft, this means shooting with the hottest feasible guns, complete with modifications and, most importantly, heavier BBs that fly through the air in a more predictable pattern. For those of you who don’t know anything about heavier BBs and physics, a heavier BB flies slower because while your projectile’s mass has increased, your gun still imparts the same amount of force to it when it fires it out the barrel. As a result, you have a slower moving projectile that hits just as hard, but is less subject to air resistance or stray gusts of wind. “Aha!” you might be thinking, “I’ll just use heavier BBs to lower my FPS and it’s all good!”

joules-formula

While that might have passed twenty years ago, but field owners and players generally have at least a passing understanding of ballistic physics these days. These days next to no one uses 0.20g BBs and as a result, every field is going to have a convenient chart that lists the joule ratings for all sorts of BB sizes in order to provide a fair, comparison between the various weights being used. As such, the true measure of how hot is too hot is Joules, a unit of measurement for force, and not FPS. Now hold onto your boonie hats, ladies and gentlemen, because we’re about to do some math. Actually, I’ll be doing some math, you’ll just be looking at this sweet chart that saves you the effort of busting out a calculator.

 

K=½MV² K (Joules) = Mass (2e-5 – 4.5e-5 kg) travelling at MPS squared (convert from FPS)
FPS / Joules 0.20g 0.25g 0.28g 0.30g 0.43g
350 1.14j 1.42j 1.59j 1.71j 2.45j
400 1.49j 1.86j 2.08j 2.23j 3.20j
450 1.88j 2.35j 2.63j 2.82j 4.04j
500 2.32j 2.90j 3.25j 3.48j 4.99j
550 2.81j 3.51j 3.93j 4.64j 6.04j


What you’re looking at here is a simple chart much like the one found at any given airsoft field in your area that isn’t just a few buddies slinging plastic in the woods or on private property. Below various weights of BB are joule ratings that correspond to that BB moving at the FPS rate of a given row. As you can see, some of these are green! At my home field, the field has a 500 FPS (with 0.20g BBs) limit, and a 0.20g BB traveling at that speed has a force of 2.32 joules. As such, if you use heavier BBs, you have a lower FPS limit so that your shots stay under 2.32 joules of force. Highlighted in green are acceptable FPS ratings for each weight of BB, while guns that fire said BBs at an FPS/weight combination that results in an amount over 2.32 joules of force are marked in red, and they would not be permitted on the field. Of special note is the black marking resulting from having a gun that shoots at 6.04j – should one’s gun shoot .43g BBs at 550 FPS, and should the RCMP ever test your guns for some reason, you may find yourself in very hot water.

Of course, if you run gas guns, there’s an added complication to all of this that you might need to consider…

Joule Creep

joules creepJoule creep is not the term for someone who’s overly fixated on the joules of his gun, although if you want to try to make that definition a thing in your local airsoft community, best of luck to you. What Joule creep really is is the term for a special circumstance that typically happens in gas powered airsoft guns. Unlike an AEG which simply spits out BBs via an air piston driven by an electric motor, gas guns propel their BBs with an excessive gust of compressed air. You may have noticed that whenever a gas powered gun is fired, there’s a large burst of air that comes surging out of the barrel. Going back to physics, a heavier object requires more energy to move. Specifically, this means that a heavier BB in a gas gun’s barrel is going to accelerate slower, which means it’s going to stay in the barrel for a longer period of time, with those explosive compressed gas forces pushing it all the while. When the BB finally exits the barrel, it will have been pushed out with more overall force than a lighter, more quickly accelerating BB that had gas propelling it for a shorter period of time.

In particular, joule creep is a notable thing when players chronograph their gas guns using a 0.20g BB, only to use heavier weighted one in actual games. They might find themselves with a gun that reaches a bit further and stings a little harder than one might expect – and when the gun is tested again by referees, it turns out that its BBs have more joules than is allowed. That said, joule creep is generally only an issue when it comes to guns that shoot close to a minimum engagement distance FPS limit or field FPS limit.

Guide to Airsoft FPS Final Thoughts

There’s a lot to think about when it comes to the FPS of your gun! Before buying any airsoft gun, be sure to know what FPS limits your location might set. Additionally, if you’re buying from outside of your country, be aware of what FPS limits your country might set and what your country’s customs might set. Finally, if you’re using a gas gun, you might have to be selective about how heavy a BB you use in games as well. Please take a look at our airsoft rifle reviews or our informative articles on our website.

C.S. Wilhelm has is a 28 year old ex-military guy who’s been playing airsoft regularly for over a year in the forests of west coast Canada. Less interestingly, he’s also a tremendous nerd. C.S. Wilhelm has a degree in both Creative Writing and English, is a former editor of Portal magazine, and is currently an IT student.