The GBBR Thread

[Airsoft-Ed]

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.

 

[TheGrover]

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

 

[Samurai]

But the heavier BB does spend more time in the barrel.

 

[Airsoft-Ed]

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.

 

[PT247]

am guessing joule creep would be less noticeable on a wide bore barrel then.

 

[Airsoft-Ed]

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.

 

[Airsoft-Ed]

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.

 

[TheGrover]

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

 

[BrightCandle]

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.

 

[TheGrover]

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

 

[CARBr6]

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

 

[CARBr6]

But bigger and louder and thus, more awesome.

And this too ^^^

 

[Wo1f]

You can get a TM mws for £430. Having owned a we 416c, unless it’s 20c or above outside, don’t bother.