joules limit

[No1_sonuk]

Re: joules limit

Also KaRcop, I think youre right, thats why some retailers have stopped selling warrior L96's/JG Bar10's online because of the high stock FPS theyre classed as air rifles and have to be sold face to face, though I THINK that only applies in Scotlant, dont quote me on that though. Whether its the actual law or just them covering their asses I dont know.

It's bowing to pressure from local police forces. If they resisted, they'd probably win if the police tried prosecuting, as there are no actual LAWS covering this, but they don't want the hassle involved.

Yeah, the thing is that the formula about energy being constant only works with a spring rifle. A spring will always push out the same amount of energy onto the bb, no matter what weight bb it is because it has a set distance that it travels and once it's finished moving forwards it stops. With a gas gun this isn't the case. The gas will keep flowing until the bb exits the barrel, causing a pressure drop.

Not entirely true.
The gas sniper releases a set amount of gas into the chamber (as it's a very short valve opening time), just like a springer does. As that's the case, it'll behave in exactly the same way as the springer. The main difference is the effects of ambient temperature and reservoir pressure on the amount and pressure of the gas released.

And for it to equal 16J with a 0.2g bb would be a ridiculous fps! I should think you're fine :-) Just so long as it's within the site limits when you're playing with it.

That limit is actually 12 ft/lb, which works out as 16.27J. That's 1323fps with a 0.2g BB.

[KaRcop]

Not entirely true.
The gas sniper releases a set amount of gas into the chamber (as it's a very short valve opening time), just like a springer does. As that's the case, it'll behave in exactly the same way as the springer. The main difference is the effects of ambient temperature and reservoir pressure on the amount and pressure of the gas released.

Hmm I'm not so sure about that. I'm 100% sure that what I said is true of GBB guns.

Realistically, there's no other way for the gas system to work other than back-pressure holding the valve open until the bb exits the barrel causing a pressure drop which allows the valve to close. The only way you could release gas for a prescribed amount of time would be to have an electronic valve or some kind of spring-loaded mechanical device that controls how long the valve is open for. Neither seem likely on an Airsoft weapon as they'd just be too expensive/complex to manufacture when there's already a good, cheap, simple, reliable system that works based on back-pressure.


How do you think your system works of releasing a set amount of gas?

[No1_sonuk]

Re: joules limit

Firstly, the OP is referring to snipers, not GBBs.

Secondly, ALL gas airsoft guns I know of (and at least 1 paintball gun - Crosman 3357)use a spring-loaded valve with inertia firing.
Simply put, the hammer spring doesn't have enough strength to hold the valve open statically, by resting on it. What happens is that the inertia of the hammer causes the valve to open due to the dynamic forces involved, but once that dynamic pressure is gone, the valve's spring (and the internal pressure in the gas reservoir) overrides the hammer spring tension, pushing the valve back against the hammer tension, closing the valve.
Presto! A VERY simple mechanical short-time release of a valve, and a hell of a lot simpler than a "back-pressure release system".

All the GBB pistols, in my armoury (TM 1911, hi-cappa, KSC M9, Maruzen PPK/S) have all the parts needed for an inertia system. I know for a fact that the only gas rifle I have, an M1892, uses inertia valve timing.

If all this were not the case, you'd not be able to leave a loaded GBB with the hammer down...

[KaRcop]

No1_sonuk, don't feel like I'm being negative against you - I'm not and there's no reason to be agitated towards me. Chill out.

I'm not talking about the valve knocker holding the gas flow valve on the magazine down. Here's my detailed reference as to the working of a GBB gun and the essence is the same across virtually any GBB gun.

http://wem4guide.wikidot.com/how-it-works

What I have said is that this system works for GBBs in terms of holding the flow valve open until the bb leaves the barrel. There is no reason why it wouldn't be used in bolt action rifles, just without the blowback (obviously).

And because of this, the gas will be applied until the bb leaves the barrel. That is why heavier BBs end up with higher energies. It's an observed phenomenon.

[No1_sonuk]

Re: joules limit

I see where you're coming from now...

What I have said is that this system works for GBBs in terms of holding the flow valve open until the bb leaves the barrel. There is no reason why it wouldn't be used in bolt action rifles, just without the blowback (obviously).

There is a very good reason, actually - it's far more complicated than needed for a single action gun.

The GBB needs to keep the gas flowing to operate the mechanism, so it needs to keep the valve open a (relatively) long time, and divert the gas after the BB leaves to operate the mechanism. The description you point to is just for GBBRs as well, which have a lot of room for the mechanism. GBB pistols are different again.

A single action gun only needs to propel the BB, so there's no need for over-complicating things with pressure-relief systems. An inertia system is FAR easier to fit in a bolt, too.

The inertia system is also basically the way most real-steel firing pins work.

BTW:
http://www.zeroin.co.uk/showthread.php?t=56924

[No1_sonuk]

Re: joules limit

Please delete

[KaRcop]

Ok, I think I understand what you mean now. Thanks :-)

But that doesn't seem (to me at the moment) to tie up with why there is a significant increase of energy when switching to a heavier bb. Just a feature of cookin' with gas?

[No1_sonuk]

Re: joules limit

Could be that the heavier BB resists the expansion more, so it has a greater effect. Kind of like gunpowder - burn it in the open and it "fizzes". Restrain it and it bangs.

A lighter BB has less inertia, so it starts to move quicker, so the pressure behind it doesn't build as much before it is released as it would behind a heavier BB.

All the guns blast some air/gas out of the muzzle after the BB. A heavier BB makes more use of the excess gas. The effect is just more noticable with a gas gun than a springer as the gas expands more and keeps expanding.

[PKR]

Re: joules limit

ive just cronoed my sniper rifle its shooting 468 on a .20 at 1.7 joules but on a .28 its 407 fps and 2.12 joules just wondering if this is actualy legal as i got a mate to shoot me with it at 5 meters just so i know what it would be like if god forbid i ever snap shot someone although ive never done so i always want to know how bad it could be to any snipers who read this please never do that to anyone as it was evily painfull

i do that with all my guns! nice to know others do the same