What scuba tank?

[Ackley Improved]

If I were to buy a scuba tank for a air rifle, what should I get? What size and BAR?

How many shots per refill on say something like a FX Storm 22cal, 29fpe..

Cheers
Trevor

[ogre6br]

300 BAR
greater than 6 litres - 8 ,10 and 12's are most common scuba that I know of

one of the main things is you have a shop who can fill to 300 BAR with the correct ultra dry air required- scuba shop with a modern filler unit should be abel to do it no problems


good to get one thats "in test" as if you aren't buying new it gives some peace of mind thats it's been pressure tested sometime in the last 2 years

some info here on where to get tanks in melb

http://ausvarmint.kjd84.com/forum/viewt ... =20&t=6616" onclick="window.open(this.href);return false;

I can work out some fills if you tell me how big the gun cyclinder is in CC

what you fill to - max pressure in gun tank- BAR

and what level you re-fill gun tank at - BAR

EG I fill to 220 BAr and fill again when pressure drops to 170 BAR or 4 magazines whichever comes first

P

[220]

Have you given any thought to a pump or are you set on a tank. I've been using a pump for my air pistol for 5 years with no drama. Easy to take with you and never runs empty.

[kjd]

Have you given any thought to a pump or are you set on a tank. I've been using a pump for my air pistol for 5 years with no drama. Easy to take with you and never runs empty.

What PSI you using though mate? pumping up 200BAR really sucks balls SCUBA is the way to go!

[220]

What PSI you using though mate? pumping up 200BAR really sucks balls SCUBA is the way to go!

200Bar even the wife can pump them up to 150Bar. All in the technique once you have straightened your arms on the down stoke bend your knees and use your bodyweight to complete the stroke instead of trying to use brute strenght. Helps if your reasonably tall.

[kjd]

What PSI you using though mate? pumping up 200BAR really sucks balls SCUBA is the way to go!

200Bar even the wife can pump them up to 150Bar. All in the technique once you have straightened your arms on the down stoke bend your knees and use your bodyweight to complete the stroke instead of trying to use brute strenght. Helps if your reasonably tall.

I guess the capacity also is a factor pumping up twice the volume to the same 200BAR has to be different. Anyway It sucks haha Give me the scuba anyday!

[220]

I guess the capacity also is a factor pumping up twice the volume to the same 200BAR has to be different. Anyway It sucks haha Give me the scuba anyday!

I don't think it would be any different just more pumping.
Yeah if there is a tank available I will use it instead of pumping but the pump is another option. I've even taken it overseas when I haven't been sure I'ld have access to a tank.

[native hunter]

Be carefule of 300's.
Regards

[Ackley Improved]

Be carefule of 300's.
Regards

Explain?

220, As for the hand pump.. they are ok, thats what I have now, but I think the tank is the go if you are going to shoot a few rounds!

Cheers
AI

[native hunter]

The only problem with 300bar tanks is the availability to fill them, very few shops do them.
Then you have the problem of over filling a rifle tank that is rated to 200bar, it will hold the pressure but may cause undue stress to the cylinder and valve fittings.
what you are really looking for is pressure not volume,in a perfect world we would all have 300bar tanks and we would get plenty of fills, but then you also need different fittings for 300bar as opposed to 232bar fittings, ones a clamp and the other a screw fitting.
I have a 232bar scuba tank and I seem to be forever getting it filled and it always settles back to less in the tank than what they state at the shop when you get them filled, this is because the air in the tank expands when it is filled due to the heat giving a false reading as to what you actually end up with when it cools and the pressure drops.
If I had a 300bar tank I would have to go to brisbane everytime I wanted it filled(450 klm round trip).
I will get one but then I will have to be careful with my fill adaptor as it is only rated to 232bar, it's an A clamp type.
Gotta be better than pumping though.
Regards

[RayG]

If I had a 300bar tank I would have to go to brisbane everytime I wanted it filled(450 klm round trip).
I will get one but then I will have to be careful with my fill adaptor as it is only rated to 232bar, it's an A clamp type.
Gotta be better than pumping though.
Regards [Quote]

NH if and when you get a 300 Bar tank you will have to change your decant fitting to a DIN unit anyway because that is the only main tank valve fitting in use on those tanks.
If whatever Dive shop you use is a proper professional he can make you a new fitting for the job and probably with your existing valve/meter bits changed over to a Din fitting for the scuba tank.
Most of the AR tanks take up to 230-250 bar safely so your 232 decant unit should be able to take the work up to 220-230bar with the usual amount of care will filling you gun bottle if you go that high in bottle pressure.
Another way to fill is to use the pressure gauge in your gun if it has one.By using the in built unit you can do away with the decant unit and go with a reducer fitting direct from the Din valve on the scuba tank to your gun and carefully use the main tank valve to fill it. FX supply this type of scuba tank fill unit as an option with most of their guns because they have the gauge built in.
There is always more than one way to shoot a cat!

[ogre6br]

The only problem with 300bar tanks is the availability to fill them, very few shops do them.
Then you have the problem of over filling a rifle tank that is rated to 200bar, it will hold the pressure but may cause undue stress to the cylinder and valve fittings.
what you are really looking for is pressure not volume,in a perfect world we would all have 300bar tanks and we would get plenty of fills, but then you also need different fittings for 300bar as opposed to 232bar fittings, ones a clamp and the other a screw fitting.
I have a 232bar scuba tank and I seem to be forever getting it filled and it always settles back to less in the tank than what they state at the shop when you get them filled, this is because the air in the tank expands when it is filled due to the heat giving a false reading as to what you actually end up with when it cools and the pressure drops.
If I had a 300bar tank I would have to go to brisbane everytime I wanted it filled(450 klm round trip).
I will get one but then I will have to be careful with my fill adaptor as it is only rated to 232bar, it's an A clamp type.
Gotta be better than pumping though.
Regards

The issues you bring up are the main reason I posted this in the top of my information

I probably should have bolded and undelined it to make sure the significance of it was understood

""one of the main things is you have a shop who can fill to 300 BAR with the correct ultra dry air required- scuba shop with a modern filler unit should be abel to do it no problems""

The problem with is 99% overcome with a water bath filling station at the dive shop
The water draws the heat away from the tank faster than the inciming fill air cna heat it up
I get between 295 and 302 Bar fill on my tank When I go to my propper shop rather than the old dive one round the corner
That is shown on the test guage on a cold (wet) tank when he's finished filling
Another way to get a fill is from the fire station- all their BreathingApp gear is 300 BAR and in the last few years they have changed over to CF wrapped tanks that need cooling while filling so they are setup for cool fill tanks.

I use a larger tank (500cc) on my Rapid than the factory supplied one ( thanks Lewis for all the effort to get me the big tank) it has a fill pressure to 250 BAR and a burst pressure much higher than that.
the standard Rapid tanks have a fill to 205 and a burst somewhere round 300

All the tanks have the pressures stamped into the tanks up near the necks.

I fill to 220 BAR- big mark on my filler so it's easy to fill to each time- and that gives me a heap of shots in my .25 cal Rapid MK2.

I have yet ot run it down to where my trajectory drops off badly and I can still get 5 x 12 shot magazines but I have never bothered to run my cyclinder that low 60 shots is a lot of hunting

Lewis has fittings for both types of tanks last tim I spoke to him- I have a spare fill adaptor for a K frame tank and it's simple to convert to a Din fitting IF Leiws is out of stock
it's really simple- just screw off the K frame and screw in th Din fitting into the fill adaptor housing

HTH

later
P

[Rabbitz]

Having filled thousands of cylinders over the past 25 odd I years I can tell you that using a water bath to cool a 300 bar cylinder during filling is next to useless (it isn't much better for other cylinders, apart from steel 72cu ft ones).

The heat generated by the compression of the gas and the expansion of the metal is just too great. There is also the fact that the thermal interface between the gas and the metal isn't that great so very little heat disapation really occurs. Some people (not me) are concerned that the temperature difference between the internal surface of the cylinder and the external surface while water cooling creates stress in the cylinder wall.

So the upshot of all this is that to do a 300bar fill it takes time. Slow slow slow fill to 300bar, then let the cylinder cool - a water bath can help here. Then once it has cooled and settled, top it back up to 300bar. Depending on the compressor, storage banks and the cylinder this may need to be repeated. Thus if you want a 300bar fill you will need to leave the cylinder at the fill station.

Oh and if the dive shop cant give you a 300bar fill, (when cooled) then find a different shop...

Rabz

[ogre6br]

Rabbitz- does a water bath make a diff with a CF tank??

I have a 6 litre CF BA tank which I use now

And mines filled in a couple of goes with a few mins cooling in between while the bloke and I have a chin wag and coffee

Truthfully I cannot tell you how long a fill takes- the BS and coffee is more important

P

[Rabbitz]

Ogre,

By CF I assume you mean the fibre wrapped jobs. They do cool faster as the cylinder itself has little mass & therefore has a smaller capacity to hold heat (thermal mass is what I guess I mean). From memory with the early Boss brand fibre wraps the manufacturer recommended the use of water baths.

One thing you need to be careful of with the wrapped steel cylinders is to make sure the paint and resin seal over the fibre is kept intact if it is to be immersed regularily. Water ingress between the fibres and steel is not the ideal situation, from a long term perspective.

As you say filling in a couple of goes, while having a cuppa ( or a beer, oops did I say that ) is the way to go. It is a funny thing that most dive shop people dont mind a chat.