I didn't know ARFCOM had an airgun sub forum. Ok then.

I have a RAW HM 1000X on order. It has a 480cc, 230 BAR tank that most people push to 250 BAR. I will be shooting 100 yard benchrest.

What is the go to for a supplimental tank? I'm looking for something that will give me 4 or 5 refills. Initially I will get refills at a nearby scuba shop. Maybe later I will get a compressor or a second tank.

With a compressor at home I could get by with one tank and refill it every time.

A SCBA tank looks like an option.

I bought an air Venturi 74cf tank and a little small tank off Amazon. I really like the small tank that fits in my backpack. But it will only give my BSA Buccaneer three fills. Sometimes four depending on how low I shoot the rifle.

1.6l tank
I like the little tank more than I thought I would. It’s got a built in check valve filling port. I wish the bigger tank had one too.

Though there are other makers, the size of Joe Brancato's Guppy (Airtanks for Sale) will do just that.  A home compressor for the Guppy does not need to be a big one. My Daystate 110 V compressor, for example, would be larger than needed.  

A 100 CU Ft SCUBA tank will also work, but you won't get complete fills.  However, you will be able to fill enough to finish a 25 shot benchrest card with sighters.  You would have to fill more often during the match than getting full fills. With a SCUBA tank at 3000 psi, you could top off at the start of a match (string) with a hand pump then fill with with the tank as needed.  I did that for quite a few years.  Though, I never have made it to the 100 yard finals at the Extreme Benchrest matches.

I also have the AV 74cf tank. They had a pretty good deal on them earlier this year. I love it. I used a hand punk for years, but now with a 300bar gun the tank is a necessity.

I got a 30 minute, 4,500 PSI SBA tank.

Going to run the gun tethered.

I have a 45 cu. ft. Air Venturi.  I get one 300 bar fill and three fills to 250 bar on my 480 cc Impact M4 tank. Then it drops down to 200 bar.  I can still shot until 2nd reg pressure is reached at 100 bar.  It takes about 15 minutes with the Yong Heng to bring Air Venturi back to 300-310 bar.

So the 45 CU is a little smaller than a 30 minute?