Super64 Posted February 7, 2015 Share Posted February 7, 2015 Thanks for the info guys, I've been away the past week so not been able to get on the forum to check the replies. I'll get the gun out at some point and check the nozzle and internals to see if anything looks broken, cheers Ed. If it is broke, is that an easy fix? Link to comment Share on other sites More sharing options...
TheGrover Posted February 8, 2015 Share Posted February 8, 2015 alrighty, tested my G5 at the range today and the new hop rubber and nub did the trick, working perfectly as designed. I also took the opportunity to chronograph the gun on the same gas using different ammo, for my own personal experiment. results as follows: 0.25g BBs: 272fps (83m/s) @ 0.8611 joules (KE) and 0.02075 kgm/s (Momentum) 0.20g BBs: 292 fps (89m/s) @ 0.7921 joules (KE) and 0.01780 kgm/s (Momentum) What this quick test shows, is that changing the ammo also changes both the kinetic energy and the momentum given to the ammo, and each by different amounts. increasing the mass of the ammo to 0.25g increases the energy of the ammo by about 8.7% and its momentum by 16.6% (double due to the fact that the Kinetic Energy of an object is the product of the velocity squared, and momentum is not) My theory explaining this is that since a heavier BB accelerates slower (resulting in the lower velocity) it spends more time in the barrel with pressure behind it; thus applying a greater impulse to the BB (since the force supplied by the pressure is independent of the speed of the BB or its acceleration) TL;DR (or the simpler conclusion) : using heaver ammo actually increases the power of the gun, so take that into consideration when measuring your FPS using anything other than a 0.20g BB Link to comment Share on other sites More sharing options...
Supporters Airsoft-Ed Posted February 8, 2015 Author Supporters Share Posted February 8, 2015 It would make a difference if I was consistently hitting higher fps than the gas powered one which this time of year is more likely as the gas is less efficient causing it to expand slower thus putting less power into each shot so the bolt hits softer. That's true, but you still wouldn't be able to hear it and say, "Ah, that's definitely running off HPA" without looking at it, could be using a higher pressure gas, using a more efficient gun etc. Thanks for the info guys, I've been away the past week so not been able to get on the forum to check the replies. I'll get the gun out at some point and check the nozzle and internals to see if anything looks broken, cheers Ed. If it is broke, is that an easy fix? Yeah it's pretty straight forward, you'd have to replace it for a new nozzle, which would involved stripping the bolt, removing the nozzle's guts (don't worry, there's only a one piece valve and a spring) and putting them in the new nozzle before reassembling everything. Only really tricky part would be if the new nozzle wasn't a smooth fit in the bolt. Some minor sanding and lubing may be required, but you could cross that bridge when you come to it. You can PM me if you need a hand, I might have some videos that can help you or something. alrighty, tested my G5 at the range today and the new hop rubber and nub did the trick, working perfectly as designed. I also took the opportunity to chronograph the gun on the same gas using different ammo, for my own personal experiment. results as follows: 0.25g BBs: 272fps (83m/s) @ 0.8611 joules (KE) and 0.02075 kgm/s (Momentum) 0.20g BBs: 292 fps (89m/s) @ 0.7921 joules (KE) and 0.01780 kgm/s (Momentum) What this quick test shows, is that changing the ammo also changes both the kinetic energy and the momentum given to the ammo, and each by different amounts. increasing the mass of the ammo to 0.25g increases the energy of the ammo by about 8.7% and its momentum by 16.6% (double due to the fact that the Kinetic Energy of an object is the product of the velocity squared, and momentum is not) My theory explaining this is that since a heavier BB accelerates slower (resulting in the lower velocity) it spends more time in the barrel with pressure behind it; thus applying a greater impulse to the BB (since the force supplied by the pressure is independent of the speed of the BB or its acceleration) TL;DR (or the simpler conclusion) : using heaver ammo actually increases the power of the gun, so take that into consideration when measuring your FPS using anything other than a 0.20g BB That is Joule Creep in effect. Heavier ammo = more power instead of the same amount at a lower velocity. Due to the amount of gas being supplied massively over-voluming the barrel. Link to comment Share on other sites More sharing options...
Supporters Samurai Posted February 8, 2015 Supporters Share Posted February 8, 2015 My theory explaining this is that since a heavier BB accelerates slower (resulting in the lower velocity) it spends more time in the barrel with pressure behind it; thus applying a greater impulse to the BB (since the force supplied by the pressure is independent of the speed of the BB or its acceleration) You are correct. Most ppl say that changing the mass shouldn't change the energy but they forget that the systems sarting point is not at the end of the barrel where we measure. The time spent in the barrel affects the different weighted projectiles differently. It's way more noticeable with GBBRs but it's the same with AEGs - but on a much smaller scale. Link to comment Share on other sites More sharing options...
Supporters Airsoft-Ed Posted February 8, 2015 Author Supporters Share Posted February 8, 2015 I tried explaining this today because the marshal at the chrono was INSISTING I chrono on .20sIt was like trying to get blood out of a stone. I ended up setting it myself and telling him another marshal had seen me. Link to comment Share on other sites More sharing options...
Supporters TheFull9 Posted February 8, 2015 Supporters Share Posted February 8, 2015 It's unfortunate a lot of people actually don't know about energy creep and think they can make their gas gun skirmish safe by putting in heavier ammo to bring down the muzzle velocity. Not realising that muzzle energy is what matters. I'd like to see retailers and manufacturers do more to address the problem in manuals/product descriptions etc because the airsoft community as a whole really needs to be made more aware of the fact that 'FPS' is not the number that matters; sites say '350 with a 0.2' for a reason and that second stipulation is what makes the difference of course. As with so many airsoft myths and chinese whispers, the fact that so many people just quote FPS numbers all the time without really understanding what they're talking about has spread a lot of mis-information amongst the community. Link to comment Share on other sites More sharing options...
Super64 Posted February 8, 2015 Share Posted February 8, 2015 Thanks Ed, not sure when I'll get round to looking properly as I'm back at work tomorrow, but if needs be I'll take you up on the offer of more help, thanks very much. Link to comment Share on other sites More sharing options...
TheGrover Posted February 9, 2015 Share Posted February 9, 2015 I tried explaining this today because the marshal at the chrono was INSISTING I chrono on .20s It was like trying to get blood out of a stone. I ended up setting it myself and telling him another marshal had seen me. To be fair, its the game site rules, if they want you to stuff a few 0.20s in a mag and test it, its not the end of the world. Ideally, the gun should be chrono'd on your ammo and the muzzle energy used as a limut (about 1.1j is the accepted standard, 350 on 0.2s) Link to comment Share on other sites More sharing options...
straffham Posted February 9, 2015 Share Posted February 9, 2015 Alpha55 banned 0.3s in GBB pistols (and presumably GBBRs, thoughI need to check) last year for precisely the reasons of joule creep. Link to comment Share on other sites More sharing options...
Guest PT247 Posted February 9, 2015 Share Posted February 9, 2015 reference joule creep, if a 0.2g BB is bang on 1.1j and 350 fps (there abouts), with heavier BBs would you eventually find a weight that would give you 350fps or will the fps always drop? Link to comment Share on other sites More sharing options...
Supporters Airsoft-Ed Posted February 9, 2015 Author Supporters Share Posted February 9, 2015 reference joule creep, if a 0.2g BB is bang on 1.1j and 350 fps (there abouts), with heavier BBs would you eventually find a weight that would give you 350fps or will the fps always drop? I had to fit a shorter barrel to my L85 because I set it for 370 on .20s and then when I loaded .28s I was still getting 370... This is why I have such a hard on for people understanding what Joule Creep is and spreading the word about it. It's also why it severely fucking pisses me off when uneducated cunts just ban gas guns because they're "dangerous" when the truth of the matter is, they're thick as pig shit and too stubborn to be educated. But yes, if I didn't know that, and hadn't changed the barrel in my L85, then I could've been shooting people with that at an indoor CQB site yesterday. I accept that sites that ban gas guns could just say, "Yeah but there are people who don't know that who come to our sites" etc etc, which is obviously true. But they're YOUR sites! Educated them at the chrono! Don't ruin it for the people who own them that do have brains for fuck's sake. That's as bad a knee jerk reaction as the handgun ban. Link to comment Share on other sites More sharing options...
TheGrover Posted February 9, 2015 Share Posted February 9, 2015 reference joule creep, if a 0.2g BB is bang on 1.1j and 350 fps (there abouts), with heavier BBs would you eventually find a weight that would give you 350fps or will the fps always drop? Perhaps so, but not according to joule creep. For the bb to get more energy, it has to spend longer in the barrel (such as if its heavier and accelerates slower), so its impossible for the heavier bb to reach the same speed. Having said that, the workings of a gbbr are much more complex and there may be other factors in play which account for Ed's experience with his L85 Link to comment Share on other sites More sharing options...
Supporters Samurai Posted February 9, 2015 Supporters Share Posted February 9, 2015 But the heavier BB does spend more time in the barrel. Link to comment Share on other sites More sharing options...
Supporters Airsoft-Ed Posted February 9, 2015 Author Supporters Share Posted February 9, 2015 Perhaps so, but not according to joule creep. For the bb to get more energy, it has to spend longer in the barrel (such as if its heavier and accelerates slower), so its impossible for the heavier bb to reach the same speed. Having said that, the workings of a gbbr are much more complex and there may be other factors in play which account for Ed's experience with his L85 The heavier BB spending more time in the barrel is precisely why the power increases. A .2 is fired out of the barrel insanely fast because it takes no energy at all to accelerate it. It's gone long before the gun can apply that much power to it. Adding weight means it takes more energy to get it moving, so it spends longer in the barrel giving the pressure more time to build. Remember that gas expands continuously. Once it's in the open air it just expands to the point where it mixes with air and disappears, but when it's in an enclosed space, it will continue to expand until it has somewhere to go. It's not like air in an AEG which gets fired down the barrel by a piston. Air doesn't expand in an AEG, imagine it like water. The BB blocks the gas's only escape route, so as long as the BB is sat in front of it, the pressure's going to go up and up. It might be possible to get a heavier shot to chrono at a higher velocity if you mess about with the barrel length/bore and ammo weight enough, my L85 was certainly close with the .28s. The reason my L85 got it so bad is because it was fitted with a 509mm 6.01mm tight bore. So it wasn't just the length causing pressure build up, but also the bore being tight as well. The gas couldn't just escape around the sides as easily as with a stock bore barrel as I imagine you have in your G5. The longer and tighter the barrel, and the greater the volume of gas being sent down it, the worse it will be. Link to comment Share on other sites More sharing options...
Guest PT247 Posted February 9, 2015 Share Posted February 9, 2015 am guessing joule creep would be less noticeable on a wide bore barrel then. Link to comment Share on other sites More sharing options...
Supporters Airsoft-Ed Posted February 9, 2015 Author Supporters Share Posted February 9, 2015 am guessing joule creep would be less noticeable on a wide bore barrel then. Yeah definitely. I've heard some people say that they needed to crank their NPAS open all the way just to get the power up high enough to be competitive with their site limits lol. Joule Creep might even be eliminated completely with a widebore because there'd be so much space around the sides of the BB for the gas to escape that the pressure just wouldn't be able to build high enough to cause it. Joule Creep happens when the gun sends more air/gas volume down the barrel than the barrel's spacial volume can contain, so if you use a tightbore you're decreasing the barrel's spacial volume, which is inviting Joule Creep to happen. You could cause Joule Creep in an AEG by using a short tightbore with a non-ported cylinder, but it would never be as bad as in a gas rifle because air doesn't expand like gas does as it isn't contained under pressure (unless it's being used in a HPA set up, of course), and it's less apparent in shorter barrels. It's just hard to cause joule creep to be noticeable in AEGs because AEG cylinders can only be so big, so adding a longer barrel is more likely to match the cylinder volume than over-volume it. Link to comment Share on other sites More sharing options...
Supporters Airsoft-Ed Posted February 11, 2015 Author Supporters Share Posted February 11, 2015 Not a rifle, but I am thinking of following this up with a rifle break down video as well, and how pistols work is largely relevant. It's essentially the same but on a smaller scale. Link to comment Share on other sites More sharing options...
TheGrover Posted February 12, 2015 Share Posted February 12, 2015 Bought a bottle of propane from El Amazonia for the weekend, got it for a tenner (inc. postage)... then found two bottles in the box almost 4 times as much as green gas for the same price Link to comment Share on other sites More sharing options...
BrightCandle Posted February 12, 2015 Share Posted February 12, 2015 Not a rifle, but I am thinking of following this up with a rifle break down video as well, and how pistols work is largely relevant. It's essentially the same but on a smaller scale. Personally I really enjoyed that video and would really love it if you did do a rifle one. I love the way the guns work and this summer I am more than ready to move to GBBR and well knowing how it all works and goes together is a big part of that for me. Link to comment Share on other sites More sharing options...
TheGrover Posted February 12, 2015 Share Posted February 12, 2015 Personally I really enjoyed that video and would really love it if you did do a rifle one. I love the way the guns work and this summer I am more than ready to move to GBBR and well knowing how it all works and goes together is a big part of that for me. Come join us on the dark side! i ave seriously considered selling my ICS L85 to make room in my gun case for another GBBR... not ready to do that though just yet Link to comment Share on other sites More sharing options...
CARBr6 Posted January 19, 2018 Share Posted January 19, 2018 On 08/01/2015 at 11:58 PM, cavninja said: a noise like and asmatic ant coughing up a fur ball This ^^^^^ One of my things is realism, it's why I use mid-cap mags, but I am desperate for a GBBR and I've begun to lust after the WE HK416D GBB as it seems to be a good compromise from the high end £500+ TM stuff at £314 I am almost certain that before 2018 is finished I will have switched from my AEG to a GBBR Link to comment Share on other sites More sharing options...
CARBr6 Posted January 19, 2018 Share Posted January 19, 2018 On 08/01/2015 at 8:08 PM, Airsoft-Ed said: But bigger and louder and thus, more awesome. And this too ^^^ Link to comment Share on other sites More sharing options...
Wo1f Posted January 19, 2018 Share Posted January 19, 2018 You can get a TM mws for £430. Having owned a we 416c, unless it’s 20c or above outside, don’t bother. Link to comment Share on other sites More sharing options...
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