FPs ok - joules too hot?

[JS101]

Hi chaps,

A new experience for me today.

I played at my usual site using my usual .25s and the same gun I’ve always used there and which has passed chrono fine before.

I had, to be fair, just changed to a Maxx hop unit and maple leaf bucking.

Today at chrono it was shooting 320-330 fps - but 1.27-1.3 Joules which was over limit.  We tried with several chronographs and got the same result.

field limit is 1.14J for Joules and (in all honesty) this was the first time I was aware that they measure J and FPS.

to be fair they let me play locked on semi (have a Titan so that’s no issue really) but this is a new one one me.

I wasn’t aware you could have FPS quite that way under the limit (even on .25s) but still be too hot on the Joules.

any idea how I can remedy?

 

[Guest]

They are two different things.

If you had a forty-tonne truck travelling at 300 fps, and a 0.2 weight bb travelling at the same speed, would they have the same energy (joules)?

Hopefully this is obvious why joules and fps are not the same thing.
 

 

[colinjallen]

I am utterly staggered that you are baffled by this.  Do you really expect that a 0.25g BB travelling at 320fps would have the same energy as a 0.20g BB travelling at the same velocity?

Where sites specify an FPS limit, they nearly always refer to the FPS on 0.20g BBs.

As to how you can remedy it, fit a less powerful spring.

 

[Druid799]

I am utterly staggered that you are baffled by this.  Do you really expect that a 0.25g BB travelling at 320fps would have the same energy as a 0.20g BB travelling at the same velocity

Rain them horses in ! Seriously condescending tone to this comment , one would hope that’s accidental ?

 

[JS101]

Errr… if you actually read what I wrote it’s clear that I understand they are two different things - what I was surprised by was the idea that FPS would be quite a bit below limit but joules still over the limit - particularly as the same gun (with the only change being the hop unit and rubber) was passed by the same site multiple times.

 

[Tackle]

Errr… if you actually read what I wrote it’s clear that I understand they are two different things - what I was surprised by was the idea that FPS would be quite a bit below limit but joules still over the limit - particularly as the same gun (with the only change being the hop unit and rubber) was passed by the same site multiple times.

Don't worry mate, some people don't know the difference between a statement & a question, it's not like you asked "wot am bestest gnu" ?. 

At a guess, when you fitted the new hop parts & reassembled, you prob drastically improved the air seal, which is obviously a good thing, easiest option is a new spring, especially if you've got a quick change box? 

 

[Badgerlicious]

The zero one calculator is a great tool to check your joules: https://www.zerooneairsoft.com/airsoft_calculator.php

energy = mass x velocity, so you up either mass or velocity your joules will go up. if you were getting 310fps before, it's not hard to jump 10+fps with better air seal, and go over the limits. 

Do you have your own chrono? I'd suggest it to anyone that wants to tweak their gun in any way, besides external attachments. 

 

[colinjallen]

Errr… if you actually read what I wrote it’s clear that I understand they are two different things - what I was surprised by was the idea that FPS would be quite a bit below limit but joules still over the limit - particularly as the same gun (with the only change being the hop unit and rubber) was passed by the same site multiple times.

Because the quoted FPS limit is with a 0.20g BB.  Your site's limit is 1.14j, which is equivalent to 350 FPS on a 0.20g BB or 313 FPS on a 0.25g BB.

As kinetic energy = 0.5 x mass x velocity x velocity, a heavier BB will have more energy at the same speed as a lighter BB.

Your upgrades have probably improved the air seal, resulting in an energy increase.

Rain them horses in ! Seriously condescending tone to this comment , one would hope that’s accidental ?

Raining horses?  That is heavy rain.

I am just frequently amazed at how little many airsofters seem to know about what most would regard as the basics.

 

[Adolf Hamster]

I am just frequently amazed at how little many airsofters seem to know about what most would regard as the basics.

i can understand where your coming from, kinetic energy as-applied to airsoft chrono'ing is literally gcse level science.

but at the same time, it is a very common misconception in this hobby, not helped by the convoluted way limits are stated mixing up metric and imperial units in the most classic of british fashions.

so it's not really all the beneficial to be too harsh on folks that get fooled by it.

 

[Rogerborg]

 

[C-Diddy]

The zero one calculator is a great tool to check your joules: https://www.zerooneairsoft.com/airsoft_calculator.php

energy = mass x velocity, so you up either mass or velocity your joules will go up. if you were getting 310fps before, it's not hard to jump 10+fps with better air seal, and go over the limits. 

Do you have your own chrono? I'd suggest it to anyone that wants to tweak their gun in any way, besides external attachments. 

Just a shame Zero One don't care enough about the limits at their own site (Ground Zero) to bother chrono-ing players. 

Agree with your suggestion of people getting their own chronographs.

 

[JS101]

I get this - and this was part of my confusion.  At the site they have a new sign that says “limit 350fps/1.14j” which, well, clearly I found confusing!

 

[Adolf Hamster]

I get this - and this was part of my confusion.  At the site they have a new sign that says “limit 350fps/1.14j” which, well, clearly I found confusing!

Its because they, like basically every site, forgot to add the "using 0.2g" caveat to their fps figure.

 

[colinjallen]

They do; however, most won't because sticking some 0.20g BBs in a mag and checking the FPS is quick and easy, whereas resetting the chrono for whatever weight BBs the player is using (assuming they are telling the truth) takes time and effort.

The reasonable middle ground is to still work in FPS but to have a chart which shows the site FPS limits for different weights.

Just a shame Zero One don't care enough about the limits at their own site (Ground Zero) to bother chrono-ing players. 

Agree with your suggestion of people getting their own chronographs.

Same with Ultimate Wargames, who I never saw chrono any weapon.

On one occasion I asked to use the site chrono to check my pistol; they did not have one.

This is also the site where, between games, they placed all weapons on the ground and then took off eye pro in the playing area.  That was great until late arriving players suddenly appeared, weapons in hand and safeties off.

Add to that allowing a player to walk around in the safe zone with a TM Scorpion slung over his shoulder with the mag in even after it was pointed out to them.

 

[Iceni]

I can't believe no one has posted an FPS chart for you.

FPS only applies to a 0.2g BB. When they quote an FPS number it is always with 0.2g. If you set your gun up to do the correct FPS with a 0.2g then when you go heavier it should automatically slow down to the new correct FPS for that BB weight. GBB guns can creep sometimes and end up hot, but for an AEG this is mostly true.


Joules on the other hand is just a measurement of energy. And more importantly the energy of the BB as it leaves the barrel. It's a more useful figure, but you still need to know how heavy the BB is.

This chart lets you visually see where those J and FPS number line up.

Take 320fps with a 0.2g BB = 0.95J.

With a 0.25g BB the energy is still 0.95J but the FPS will now be about 285FPS.



For your example you were shooting a 0.25g BB at 330fps = 1.26J

So the converse 1.26J for 0.2g is = 365FPS.


I hope that sort this out for you.

 

[Rogerborg]

I get this - and this was part of my confusion.  At the site they have a new sign that says “limit 350fps/1.14j” which, well, clearly I found confusing!

Honestly, I don't blame you.  It's up to sites to explain what they mean, and far too many don't bother.  They're stuck still thinking in terms of everyone using 0.2g BBs, to the point of not even specifying that, when essentially nobody is using BBs that light in woodland any more.

At least they had a Joules figure up there, which is still better than some places.  But it makes the fps irrelevant, because what they really mean is 1.14J with whatever ammo you're using, and that happens to be 350fps if you're using 0.2g (but you almost certainly won't be, so it's a pointless number).

There's an argument that it's simpler to communicate one big round number than one small one, but it's facile since you have to convert the big number to the small one for it to be any use.

Then they'll argue that it's quicker to chrono with site 0.2g BBs (if they bother chronoing, or checking for it), which is great until you see just how much even AEGs can Joule creep with heavier ammo.  I had a bit of a surprise yesterday when my AEG jumped from 1.1J up to 1.2J just by going from 0.25g to 0.32g with no other changes.  Fortunately that was bang on the site limit.

And I honestly couldn't tell you what fps it was seeing with either weight, because it's an irrelevant number.  You set the chrono to the BB mass, and you look at the Joules figure, done.  Alternatively you can use a chart to convert from fps to Joules, but why bother when it's a few presses on the chrono for most common ammo weights?

And credit to this site (Area-66), they even announced that if anyone changed BB weight during the day that they should get re-chronoed. That's the way that sites should be thinking and communicating now.

 

[colinjallen]

A simple table showing the equivalent FPS at different BB weights for sites that have limits of 350FPS and 360FPS on a 0.20g BB; numbers are rounded down.

View attachment 80358

Honestly, I don't blame you.  It's up to sites to explain what they mean, and far too many don't bother.  They're stuck still thinking in terms of everyone using 0.2g BBs, to the point of not even specifying that, when essentially nobody is using BBs that light in woodland any more.

At least they had a Joules figure up there, which is still better than some places.  But it makes the fps irrelevant, because what they really mean is 1.14J with whatever ammo you're using, and that happens to be 350fps if you're using 0.2g (but you almost certainly won't be, so it's a pointless number).

There's an argument that it's simpler to communicate one big round number than one small one, but it's facile since you have to convert the big number to the small one for it to be any use.

Then they'll argue that it's quicker to chrono with site 0.2g BBs (if they bother chronoing, or checking for it), which is great until you see just how much even AEGs can Joule creep with heavier ammo.  I had a bit of a surprise yesterday when my AEG jumped from 1.1J up to 1.2J just by going from 0.25g to 0.32g with no other changes.  Fortunately that was bang on the site limit.

And I honestly couldn't tell you what fps it was seeing with either weight, because it's an irrelevant number.  You set the chrono to the BB mass, and you look at the Joules figure, done.  Alternatively you can use a chart to convert from fps to Joules, but why bother when it's a few presses on the chrono for most common ammo weights?

And credit to this site (Area-66), they even announced that if anyone changed BB weight during the day that they should get re-chronoed. That's the way that sites should be thinking and communicating now.

The issue is that sites just want to get chronoing done as quickly as possible so do not want to spend time changing the BB weight setting on the chrono; in addition, most marshals that I worked with or have seen do not know how to.

 

[SBoardley]

Honestly, I don't blame you.  It's up to sites to explain what they mean, and far too many don't bother.  They're stuck still thinking in terms of everyone using 0.2g BBs, to the point of not even specifying that, when essentially nobody is using BBs that light in woodland any more.

At least they had a Joules figure up there, which is still better than some places.  But it makes the fps irrelevant, because what they really mean is 1.14J with whatever ammo you're using, and that happens to be 350fps if you're using 0.2g (but you almost certainly won't be, so it's a pointless number).

There's an argument that it's simpler to communicate one big round number than one small one, but it's facile since you have to convert the big number to the small one for it to be any use.

Then they'll argue that it's quicker to chrono with site 0.2g BBs (if they bother chronoing, or checking for it), which is great until you see just how much even AEGs can Joule creep with heavier ammo.  I had a bit of a surprise yesterday when my AEG jumped from 1.1J up to 1.2J just by going from 0.25g to 0.32g with no other changes.  Fortunately that was bang on the site limit.

And I honestly couldn't tell you what fps it was seeing with either weight, because it's an irrelevant number.  You set the chrono to the BB mass, and you look at the Joules figure, done.  Alternatively you can use a chart to convert from fps to Joules, but why bother when it's a few presses on the chrono for most common ammo weights?

And credit to this site (Area-66), they even announced that if anyone changed BB weight during the day that they should get re-chronoed. That's the way that sites should be thinking and communicating now.

I’m sorry but I tend to slightly disagree with your assumption. 
as I understand it , the law states the joule rating based on 0.2g bb. So if any of my auto capable rifs shoot under 1.14 joules, they meet the legal bench mark, irrespective of whether I use .12g or .36g bbs. 
edit. Well it’s actually 1.3 joules I believe but most sites like the 350 fps thing. 

 

[Adolf Hamster]

The issue is that sites just want to get chronoing done as quickly as possible so do not want to spend time changing the BB weight setting on the chrono; in addition, most marshals that I worked with or have seen do not know how to.

not to mention the number of sites that'll set the chrono to the correct weight, then read the fps value instead of the joule value anyway.....

 

[colinjallen]

I’m sorry but I tend to slightly disagree with your assumption. 
as I understand it , the law states the joule rating based on 0.2g bb. So if any of my auto capable rifs shoot under 1.14 joules, they meet the legal bench mark, irrespective of whether I use .12g or .36g bbs. 
edit. Well it’s actually 1.3 joules I believe but most sites like the 350 fps thing. 

The law does not mention weight, only energy:
 

The permitted kinetic energy level is—

(a)in the case of a weapon which is capable of discharging two or more missiles successively without repeated pressure on the trigger, 1.3 joules;

(b)in any other case, 2.5 joules.”

not to mention the number of sites that'll set the chrono to the correct weight, then read the fps value instead of the joule value anyway.....

Indeed; I just put it down to...humans.