Scuba tank?

[Alderman]

I have a chance to purchase a 3500 psi 100 cf scuba tank with current hydro and fill for a good price. 

I will be using it to top a gun off from 100 to 175 bar. I was looking at 4500 psi SCBA tanks but the cost will be twice as much for a tank with just a few years before it expires. 

Other than the excessive weight of the scuba tank will it be feasible for what I want to do? I believe the gun has a 240-288 cubic inch tank and the previous owner says it shoots best from 175-100 bar even though it will take a fill to 200 bar.

i spoke with the local scuba shop and they will fill the tank for $5 and they do their own in house visual and hydro tests.

 

[JW652]

If it is a steel tank (reputable brand), at a good price, you will probably be very happy. They are very durable and last a looong time. 

 

[Franklink]

http://calc.sikes.us/

Lloyd has a calculator on that site that will give you an idea of how many fills you'll get. 

It's really all about top end fill pressure. 175 bar is 2538psi. So you'll only get complete fills to 175 bar until the tank gets down to 2538psi. In this case, from 3500 down to 2538, youll get complete fills. Every fill after that will be less than complete (fewer shots cuz it fills the gun to 174 bar, then the next time 173 bar, then the next time 172 bar then the next time 170 bar, etc). 

Then you've got the local scuba shop. They'll fill til the gauge shows 3500, when hot. But as soon as that cools off you'll be down around 3300psi, so you're already fewer complete fills of the gun. 

SCUBA can be used by airgunners, but really, SCBAs are the better option.

Here's a little write-up I did of my adventures with this. (Yeah, I bought a SCUBA first, but eventually needed an SCBA). 

https://www.airgunnation.com/topic/home-cascade-system/

 

[5thumbs]

Alderman, Any chance your in California near SF? If so I have a SCUBA tank you can have. It will need a hydro, but the local fire extinguisher place does them for $30 or $35. I used to use it to fill my Discovery rifles.

 

[JohnL57]

It depends on how much you shoot in my opinion. If you mainly hunt and pest you just don't get that many shot opportunities (typically) so once you have your holdovers and optimum fill pressure figured out, you won't need that much air. If benchrest or paper punching is your purpose then an SCBA tank would probably be a better choice.

OR multiple scuba tanks-then you can use the tank with the least air to fill as high as it will go, then top off with the higher pressure tank. When the tank with the least air drops below minimum fill pressure for you gun, get it refilled. Use the other tank to fill and then top off with the newly filled tank. It's called cascading and works well in my experience. 

 

[Alderman]

When I was on the fire department we filled the SCBA tanks while they were in a cold water bath. Does a dive shop do this when they fill tank?