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Old 03-31-2020, 03:19 PM   #1
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How do you actually find out about the joules and FPS

Hi all I’ve been struggling recently to understand how i actually would measure the joules or FPS as I don’t k ow if your supposed to shoot in a .2 and if it’s under 500 FPS which my site has max if 500 FPS your all good to go or do you have to be under FPS because if you use a heavy bb the FPS will increase and may be over 500 sorry for bad explanation I just don’t really understand
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Old 03-31-2020, 03:41 PM   #2
Fynn64   Fynn64 is offline
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Heavier bbs move slower than lighter ones, therefore if your fps limit is 500fps with 0.2g bbs, you will be fine with using heavier ones.
The Joules are calculated like this:
E=1/2*m*v^2( E: energy , m: bb weight, v: bb velocity).
Theres also stuff like joule creep, but I‘m not gonna get into that now...
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Old 03-31-2020, 04:41 PM   #3
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Old 03-31-2020, 05:03 PM   #4
Sodium   Sodium is offline
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Joules are a measure of a projectiles energy. To explain this in real world terms, shoot an airsoft bb from a airsoft pistol at like 350 fps. That bb has a mass of 3 grams. The energy in the bb, kinetic energy (energy of motion) can be calculated using (1/2)*mass*velocity squared. Doing the math using an online kinetic energy calculator, there is 1.13J of energy in the bbs motion.

Now imagine you throw a baseball as hard as you can. If you throw it at 70mph (100 fps,) it may be going a lot slower, that it will hit wayy harder as it has a ton more energy. Since it weighs 150 grams, plugging in the numbers, it's traveling at a wopping 34J!! It's slower, but it's way heavier to it hits harder. Its the difference between hitting someone with a wet noodle and a crowbar.

So regarding your field limit of 500fps with .2g bbs, how hard your rifle should be shooting is really up for debate. Technically because they measure in fps at a single weight, as long as your rifle is following that specific guideline, you are legally playing within the rules.

The issue here lies in a thing called joule creep. Heavier bbs generally gain more energy from the system than lighter. 500 fps with .2g bbs is 2.32 joules, but if gou shoot .48g bbs, depending on how your settup is built, it may be outputting far more, maybe even closer to 3J. The heavier bb literally has more energy in it in this case, and this is where the controversy lies.

Many fields these days are switching to joule limits instead of fps limits. This meanz they are checking the energy on the weight you will use rather than just the fps of a lighter bb, as that fps really isn't representative of how hard your rifle is shooting.

In my opinion, make sure your rifle is hitting less than 500fps with .2g bbs and thats it. Assuming you guys have a minimum engagement distance, even if with the weight you are using you have a lot more energy, you shouldn't be shooting close enough for people to get hurt anyways; they'll be fine. As a sniper, limiting yourself to bolt action is already enough of a disadvantage, and I would say to try and get advantage within the rules that you can, as long as you are not endangering others (which you aren't at closer to 3J. More likely about 2.6J though.)

Once you have read all that, you may want to look into joule creep a little more, as that is really the crux of your question.
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Old 03-31-2020, 05:46 PM   #5
 
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The easy way to find out what your rifle is shooting in both FPS and Joules, is to get a chronograph that will output the Joules. Like one of these 2.

https://www.evike.com/products/55335/

https://www.evike.com/products/60352/

Having a chronograph in your tool collection is essential as a tech, anyone who doesnt have one who calls themselves a tech is straight up full of it and should not be trusted.
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