How do I know how much gas is left in a mag?

[Slodin]

Hi,

I bought a KJW M9, with a metal slide and this is my first airsoft pistol. Upon reading maintenance for general use of gas pistols, it's advised to keep some gas in the mag. (green gas, or silicone propane) But not at a full charge..

The mags I have are fresh and new, so I charged them about 3seconds, and shot around 10bbs from each to test fire for feeding and blow back features. I'm using silicon oil + propane to fire my pistol. (I have a small backyard, so I decided to stop since it's really easy to spot me shooting, and inside the building is a nono for the propane mag, it smells)

Upon reading that post, I'm suppose to leave a tiny amount, but how much is "tiny"? and how would I know how much to leave it at since I have no idea how much gas it's left in the mag.

any input would be great.
Thanks

[Red Dot]

I leave it wherever it's at, like you said you have no idea. I just read that it's a bad idea to discharge your gas mags by pressing open the valve so I just don't do that. So far I've had my pistol for about 9 months and no leaks even keeping them at a full charge.

[jordan7831]

Enough gas for one or two shots is the enough amount. But people have said that a little gas. Or full charge of gas puts relatively the same pressure on the valves. So half a second is usually enough for a shit or two. But keeping them charged won't really hurt the mags either.

[MultipleParadox]

I never really cared about the amount of gas left, as long as they're not empty for a prolonged time; more often than not leaving them at full charge

It never occasioned any particular problems

That's with 30ish gas mags now (pistols, smg, carbines..)

[cetane]

If you feel pressure on the discharge valve it's enough gas. I usually leave them full filled...

[DipTwit]

The danger in leaving them full is that, if they are left in a hot environment (car / trunk on a hot day, or leave your bag in a room with sun hitting it through the window) the gas pressure will increase, in some cases until the magazine deforms. I've had 2 magazines do this, in my case deforming at the bottom end where metal pins try to hold the end 'cap' or 'door' against the rubber bottom seal. Repairing a magazine from this can be done in some cases, but leaves the metal weakened.

The reason some people say the pressure is similar no matter how full, is that propane is usually stored in the magazine compressed in *liquid* form (that's why you fill with the propane bottle upside-down, to get the liquid at the bottom. As long as there is liquid, that liquid will vaporize to equal out the pressure, so the pressure inside the magazine is *almost* the same right up until the liquid runs out, then as the gas escapes the pressure goes down quickly.

While this evenness of pressure makes for consistent shots (hence why propane / green gas is preferable to, say, CO2 which doesn't liquify at the pressures we use) it means you have to *almost* empty your magazine if you want to guarantee not to have deformed magazines.

So, to do this, you would completely empty your magazine (slowly, maybe by firing the gun. Opening the release valve is only bad because it cools the magazine *really* fast which isn't great for the metal) then put some green gas / propane in but this time DON'T turn the bottle upside-down, do it right-side-up, allowing just vapor to enter the magazine. You could even fire it once or twice after that to ensure there is only partial pressure in it.

Of course, you can protect your magazines by controlling their environment - keep them in a cool basement for example, and they should be just fine there too. That's probably what most of us do, since your house is probably at a pretty constant temperature all the time.

Hope that helps!

[Ricochet]

Originally Posted by cetane

If you feel pressure on the discharge valve it's enough gas. I usually leave them full filled...

^
This

Leaving magazines empty has never failed to make them leaky after just a few weeks. I've never had a magazine deform, but I don't leave then lying in the sun. Then again, I don't leave bottles of green gas, propane, or anything else that's under pressure in direct sunlight either. I have always left mine half full to full. Give a gentle push to the discharge valve, on the back of the magazine, if you can't push it in easily, then there is gas in there. If it pushes in, then there is none, and if gas comes spewing out, you pushed too hard. lol

[Slodin]

ok, thanks everyone for the input.
I do keep all my equipment in the basement which is generally really cool..
my friends have to put on jackets to stay in here in the summer lol..I got use to the cold..

So temperature should not matter for me even leaving at full charge which it's always pretty cool down here..(of course I won't keep it at full charge..probably just half charged after a game or something)

[MultipleParadox]

You don't even have to keep them in the cold if at full charge
Just don't leave them in the sun or an oven (trunk or in a car while 25 degrees + for exemple)

Beside that, there's really no stress to have about this. It's just a matter of common sense

[jordan7831]

Hank Hill would be proud of this post.

Originally Posted by DipTwit

The reason some people say the pressure is similar no matter how full, is that propane is usually stored in the magazine compressed in *liquid* form (that's why you fill with the propane bottle upside-down, to get the liquid at the bottom. As long as there is liquid, that liquid will vaporize to equal out the pressure, so the pressure inside the magazine is *almost* the same right up until the liquid runs out, then as the gas escapes the pressure goes down quickly.

While this evenness of pressure makes for consistent shots (hence why propane / green gas is preferable to, say, CO2 which doesn't liquify at the pressures we use) it means you have to *almost* empty your magazine if you want to guarantee not to have deformed magazines.

So, to do this, you would completely empty your magazine (slowly, maybe by firing the gun. Opening the release valve is only bad because it cools the magazine *really* fast which isn't great for the metal) then put some green gas / propane in but this time DON'T turn the bottle upside-down, do it right-side-up, allowing just vapor to enter the magazine. You could even fire it once or twice after that to ensure there is only partial pressure in it.

Of course, you can protect your magazines by controlling their environment - keep them in a cool basement for example, and they should be just fine there too. That's probably what most of us do, since your house is probably at a pretty constant temperature all the time.

Hope that helps!

[GR]

So let me get this straight... It's actually worse to keep a completely empty magazine with no gas, and that it is harmful to the mag if I use valve release button?

I've owned a Glock 17 for about 4 months now, and I made sure every time before I store it I use the valve button to release all the gas to make sure that valves are not under pressure...

Was I doing it wrong the entire time?! D:

[DipTwit]

You may find rubber o-rings in an empty mag dry out on you - lots of people have experienced this, so they keep a little pressure (and possibly traces of silicon oil) on the valves. This is not an emergency thing, as an o-ring (or the entire valve) isn't crazy to replace if it does go.

Rapidly cooling the metal by opening the release valve isn't doing anything that firing the gun doesn't do, it just does it more & faster. Whether you can accept a little more wear on your magazine is up to you - it's not going to ruin it overnight, but some people like to get technical (oh damn, that's me) and do the best they can for their equipment. I wouldn't worry about it, you mag could theoretically live longer than you

[FirestormX]

Is the cold really a problem for the metal? My concern is always the orings freezing, getting brittle, condensing, and so on.

[Slodin]

Originally Posted by DipTwit

You may find rubber o-rings in an empty mag dry out on you - lots of people have experienced this, so they keep a little pressure (and possibly traces of silicon oil) on the valves. This is not an emergency thing, as an o-ring (or the entire valve) isn't crazy to replace if it does go.

Rapidly cooling the metal by opening the release valve isn't doing anything that firing the gun doesn't do, it just does it more & faster. Whether you can accept a little more wear on your magazine is up to you - it's not going to ruin it overnight, but some people like to get technical (oh damn, that's me) and do the best they can for their equipment. I wouldn't worry about it, you mag could theoretically live longer than you

it's no doubt that metal would out live me..
but whether it's functional by that time is the question LOL

[DipTwit]

Originally Posted by FirestormX

Is the cold really a problem for the metal? My concern is always the orings freezing, getting brittle, condensing, and so on.

I'd guess all of those are good reasons, even if they're not life or death. Rapid heating / cooling cycles can play havoc on metal, but we're not building space shuttles here either...