FPS vs Joule
 

Hey guys so I got a VFC Sr15 and got it fully upgraded nothing is stock anymore. so I was wondering what is the best BB weight with .20BB I'm shooting 399 Fps and 1.48 joule. With a .33BB Im getting 327 FPS and a 1.64 joule. What is better FPS or the Joule is there an ideal weight? thanks for the help

Keep your FPS and joules within the local rules and then choose the heaviest weight of BB you can that performs well. FPS and joules can be easily calculated by using easy to find graphs online.

All fields use muzzle energy limits, not fps limits.
When a limit is "400fps on a .20" that's actually an energy limit.
When a limit is "420fps" it is just implied that it is measured with .20g BBs, and is still an energy limit.
Be aware of what your local field limits are and stay within them.

As for performance, the rule of thumb is to use the heaviest BB possible without losing range. That will give you the best range and accuracy.

FPS is more important for CQB than field use. Lighter BBs lose their velocity faster, and have less accuracy. In field use, it's more important that the BB get further away and accurately. And since heavier BBs lose their energy less quickly, it's possible for a .30g BB to pass a .25g BB in flight after 200ft or so.

400 with a .2 IS 1.48 J it's easier to remember and understand 400 fps as a limit though. Everyone should technically be chronoing with the weight they are shooting in order to determine they are actually under a predetermined limit. It's just easy to do with .2s because they are cheap. However, as you see with your .33s, it doesn't scale in a linear fashion due to science.

you cannot exceed 1.48 J with ANY weight.

If you are shooting higher J with heavier weight then that is an issue and your gun will not make chrono as it shoots over the limit. The fps at .2 is irrelevant. It's the Joule it shoots with whatever weight you are going to use that has to be 1.48. (if 400 is your local limit)

I would like see a complete switch to joules in Ontario. Measuring with FPS is like using the imperial system instead of metric. Sure, some people find it more intuitive... but its a bad system both in theory and practice...

Yes joules over FPS, though it is good to understand and relate to both. Unfortunately I seem to find a lot of people who lie about the weight they are using as it is easy to do. 0.20g is a great baseline to compare with other weight rounds, because as mentioned above, ANY BB out of your gun should be under the limit. No, it's not okay to swear up and down that you won't change round weights. Your gun must shot under for any weight at any time, or turn it down below the limit.

Are people just checking velocity and totally ignoring BB weight or what?

Fps is literally half the information required to determine muzzle energy. So more realistically; measuring with fps is more like measuring weight when determining mass.
Easy enough to determine mass from weight when you know the gravitational constant at a given altitude.

What I do is write the max fps for each weight on the chrono because its way faster than reprogramming the chrono for every player. And I think the xcortechs calculations are off for muzzle energy anyway.

399 with a .42. lol I'm under 400.

I know CTF around calgary hear usually doesnt check weight. Gotta give everyone an equal chance to dodge BBs lol

Lots of fields I've been over the years Chrono with .2s provided by the ref... And that's it. It's specially problematic with how much more popular GBBR s and HPA systems have become as opposed to a few years. Hell, people even over volume AEGs for that joule creep effect. I do like the system theyve got at siege with multiple bb weights readily available

Simplest method would be just to chrono on .28s or .30s as opposed to .20s
You're not getting the most accuracy, but you're way more accurate than you would be with .20s
Best part is, if someone IS using .20s and they're reverse creeping, it's not actually that big a deal.
Like If they're shooting 1.48j on .30s, but 2j on .20s, the .20s lose energy so fast it won't be anywhere near as dangerous as the opposite effect.

Most I've been able to creep an AEG is about .1J and that's even hard to confirm because I don't have a scale that can weigh bbs down the 100th of a gram. You could argue that amount of variance can occur in the other variables caused by the gun such as a tiny leak or failure of the nozzle to completely seal against the bucking lips, the sphericalness of the bb itself, weight variance of the bbs. Research into the ammo I was shooting was that the .32s I was shooting actually weighed closer to .31, so my higher fps reading could have been a result of lighter than expected ammo, thus throwing off my J numbers. But long story short, it's hard to get an AEG to creep significantly that it would be noticeable in range or precision. 10-20fps more than expected is not going to win you a game.

Hell what did the 400 vs 500 fps test yield in overall range difference? like 30 feet or something not that substantial.

But have you specifically been building guns FOR joule creep? Lol
You cant make energy out of nothing, so its more accurate to say that joule creep is the effect of losing energy on lighter rounds because the gun is overvolumed for lighter BBs.

Using .30s at 1.48j vs 2j wont make a big difference.
But shooting 1.48j on .30s and 2j on .43s, you can bet theres gonna be a MAJOR advantage in range and accuracy.

Insurance sets the limits, and thus the standard. , 1.5 Joules.
We post that, and the equivalent FPS for all major bb sizes at every Crono.

You can get really good/ Great distances at 1.5 or less. with
the right set up

Energy [Joules] = 0.5 * Weight [kg] * (Velocity [m/s])^2
Example:
W = 0.2 g = 0.0002 kg
V = 399 FPS = 121.615 m/s
E = 0.5 * 0.0002 * (121.615)^2
E = 1.479 Joules

For some MilSim's at PRZ they had 400FPS for AEG's using 0.2g.

For HPA and GBBR you had to chrono with a 0.4g BB and shoot under 1.5j.

I don't know why the fuck people are so biased. I know as well as anyone that HPA can joule creep like mad, but so can an AEG.
Someone purpose built a gun as a demo that shot 1.6j on .20s and 3.2j on .45s

Because one in a hundred AEGs creep (not an exact stat), and only with a certain setup you don’t need to have. EVERY HPA unit creeps, and not just with slight effect, but many don’t lose ANY velocity with heavier weight rounds. In fact, some gain velocity once crossing up over a certain weight. So your creep ability is not just there, but always high and easiest to abuse out of every platform. AEGs that creep rarely climb much above the joule standard, just a slow increase per BB weight.

Here’s a real example of HPA creeping:

- HPA unit on 0.20g = 2.26 joules
- HPA unit on 0.40g = 2.69 joules

That’s huge and retarded.


Here’s a real example of AEG creeping:
- AEG unit on 0.20g = 0.95 joules
- AEG unit on 0.40g = 0.97 joules

There’s worse examples, but nothing like HPA or the worst GBBR for that matter.

Swap into the wrong mag, or the temperature goes up and your gun jumps WAY above field limits. That’s without trying to cheat or doing it on purpose.

EVERY gun, when it steps on the field after morning chrono, should be set to handle all BB weights and temperatures without going over the field joule limits. It’s the gun owner’s responsibility to make certain this is the case.

Why bother chronoing AEGs on .20s though?
Its not accurate, and if someone does want to cheat by abusing joule creep then you're asking them to use AEGs.
If you chrono everything on .30s, you only need 1 bag, 1 fps scale, 1 method.
Simplifies everything, and makes it more accurate.

It’s fairly accurate for AEGs, but there’s a lot of HPA users running 0.36 to 0.46 BBs. Also, we’re talking about holding all guns to the same field standards, not cheaters. Someone can still adjust their gun after chrono. That’s a separate issue.