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Airsoft Guns- How FPS, Joules and BB Weight Effect Accuracy
 
 

*Note: This FAQ is to describe how airsoft BB's can affect FPS, Joules and the trajectory of your shot. It is also recommended that you have a Calculator on hand*

Lets start off with some of the acronyms and terms you will see during this FAQ.

FPS: Stands for Feet per Second, classifies the power of any gun.

CQB: Close Quarters Battle also referred to as CQC or Close Quarters Combat.

Joules: Also a way to calculate the power of an air-soft gun. This is more accurate than FPS is.

AEG: Automatic Electric Gun.

How to gauge the power of your airsoft gun:

By FPS:
The easiest way to gauge the power of your airsoft rifle or pistol is by checking the FPS. Our website tells you what the FPS is on each model of airsoft gun. These are averages, not exact. Many forces (mainly gravity and friction) act against the BB and will cause the FPS to drop considerably as soon as it leaves the barrel of the gun. FPS is how many consumers, manufacturers and the worlds governments gauge and regulate air-soft guns. Because of it’s easy to understand nature this system has been widely accepted world wide and is used by many.

A high grade air soft gun will usually have a higher FPS than a lower quality clone but this doesn't always apply.

FPS also increases and decreases with what weight of BB you use. Examples are as follow:

380 FPS with .12 Gram BB’s
350 FPS with .20 Gram BB’s
335 FPS with .23 Gram BB’s
320 FPS with .25 Gram BB’s
315 FPS with .28 Gram BB’s
300 FPS with .30 Gram BB’s

As soon as the BB leaves the barrel, because there is no more force acting against the BB and it will begin decrease in speed dramatically. Its also a good idea that after 50 feet to subtract 100 to 150 FPS from your equation. FPS can also be affected by the environment including wind, air, and barometric pressure that can affect FPS.

We recommend only using .20 to .25 gram BB’s in your standard AEG (Automatic Electric Gun) to increase, accuracy, performance and lengthen the life of your gun. .28 and .30 gram are meant for upgraded AEG’s and Sniper Rifle style of airsoft gun.

You will see that .12 holds the fastest speed and .30 has the slowest. Keep in mind that even though one is traveling faster than the other they will both travel the same line, on average to the same spot. However, the lighter BB will get there faster and the heavier BB will have more energy stored in it making it go slightly further.

The easiest way to measure the FPS of your airsoft gun is to use a Chronograph to gauge its speed. A Chronograph uses light to track the speed of the BB leaving the barrel of the gun from one point to another.

Keep in mind that many airsoft guns need seasoning or breaking into shoot at the FPS that the manufacturer or the merchant has set forth. It is a good idea to put at least 300 rounds through the gun the get to its true potential.

We will talk more about the exact difference of weights in BB’s later in this FAQ.

Joules:
Joules is another way to calculate the power of your gun. A Joule is a measurement of energy and is stored in every BB. Different weights of BB's can also hold a certain amount of energy even though they are made of plastic or biodegradable ingredients and are the same size as its lighter or heavier counterparts.

You will normally not see Joules as a form of measuring power on many website because it is much more complex and uses a mathematical equation to find out the amount stored in each BB. Unlike FPS, Joules will stay at a constant in conditions with harsh winds and days with clear sky and no breeze.

To find out your Joules, you will first need to turn your Feet per Second into Meter Per Second using the mathematical equation.

M=F x 0.3048
M= Meters
F= Feet

Then turn your Grams into Kilograms using this equation.

Kg=.001 x G
G= Grams
Kg= Kilograms

The Equation that is used now for you to get the amount of Joules in each shot is this.

E=½ x M x V^2
E= Joules
M= mass in kilograms
V= velocity in meters per second

We will use 270 FPS and .20g BB in this example equation:

275 x .3048 = 83.82 Meters per Second
.001 x .20 = .0002 Kilograms
½ x .0002 x 83.82^2 = 0.702579

So in a .20 gram BB going at 275 FPS carries 0.702579 Joules of energy in each shot.

By measuring your airsoft guns power in Joules you can get a better feel for how accurate and powerful your gun is. An airsoft gun that shoots at 380 FPS with 3J hits much harder than one that shoots 380 FPS with 1J, so please take safety into account. Use a trial by fire method, would you want to be shot by your own gun? If you wouldn't like it, I doubt your friends or other players would like it as well.

Now that I have confused you enough let me sum up what just happened. The FPS effect’s your Joules which are affected by the weight of your BB. So the heavier the BB the more energy in the BB giving it more force so it can travel longer and straighter (and it will hurt more!)

How a BB can affect your shot:

It is simple rule of thumb to never use .12 BB’s in AEG and High Power Spring air-soft guns. Because of there low quality they can break inside the gun damaging your air-soft gun or even destroying it if there was a jam. .12 gram airsoft BB's are also not seamless and may contain a lot of burrs (defects). The BB's you usually get at your local sporting goods store are .12 gram unless they specify heavy weight and the amount of Grams. Even though the price for .12 gram BB’s are tempting it’s not worth ruining your gun to save a few bucks.

When we say we recommend that you use .20 to .25 grams it really is for the better. This is one of the reasons we do not carry .12 gram BB’s. We only want to carry quality product in our warehouse for our customers to use.

You may be thinking, "If it lowers my FPS, what’s so good about a heavier BB?"

There are several different reasons why a heavier BB is better. If you were to compare a .12 to a .20 BB you would notice on the .12 BB a seam in the center of that circles the entire BB and a burr on the top where the plastic is injected into the mold to form the round. The .20 (or higher) will not have this, there will be no seams or a burr on the top that will make the BB inaccurate or cause your gun to jam. The seam and burr creates weak points on the BB making it more liable to shatter on impact or in the gun. These also throw off the trajectory and balance of each BB making them non-uniform and highly disliked by many players.

With .28 or higher you are looking at a very heavy weight BB. We only recommend that you use these BB’s in upgraded or higher end models that use all metal construction and tight bore barrels. .28 and higher may not also feed in to some guns so you need to be careful. The last thing you want is a jam that could possibly ruin your gun.

With the difference in the weight of each BB you will also get different amounts of resistance to wind and barometric pressure. The lighter the BB the more likely the wind will grab it throwing it off course making the shots inaccurate. The speed of the BB does not affect the accuracy, just how fast it will get from the barrel to the target. Heavier BB’s will be able to have lest resistance with wind and will mainly travel straighter and farther than a lighter BB.

Remember if you do have a jam, do not continue pulling the trigger. You could destroy the gears and pistons by stripping them which means you are looking at expensive repairs or buying a new air-soft gun because this is not covered by any manufacturer warranty. It is best to stop shooting, remove the magazine and battery and take the unjamming rod and push the BB out and then feed one BB in at a time to make sure everything is working correctly before going out to play.

How all of these will affect one another:

Now that you know and understand the how FPS and Joules work together as well as how a BB and your environment can affect your shot. All these things need work in conjunction with one another. FPS tells you how fast the BB is going, Joules tell you how much energy is stored in it and how uniform each shot is, while the brand and weight of BB affects both of these.

 
 
 
 
 
 
 
 
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