Welcome to the forum Johnny
A 12 L dive bottle, and shooting little not too powerful stuff, even being a avid shooter you will have many many many hours of shooting fun.
But you should shoot tethered to the large bottle then, so have to make sure your big bottle do not have more pressure than rifle like.
Being .177 shooter when i did not have my own compressor i could still shoot for a month before my 12 L bottle pressure was down from 300 BAR to 150 or so ( shoot with less than 100 BAR pressure on the regulator, i have long rifle so light stuff like 10 grain i can shoot with the minimum my rifle can regulate to, and that is 56 BAR )
If you do not shoot tethered and fill every now and then, you for sure want to fill to a larger pressure every time, and so you will probably not shoot your big bottle down to a that low pressure.
CUZ if you only fill little gun tank to say 170 BAR well you will not get very many shots in a fill VS saying filling all the way to the 250 or 300 BAR the rifle can handle.
Just one problem in Denmark, Dive shops here will not fill any bottle to 300 BAR for some reason, even if their compressor can easy handle that.
Also some fill to, but then do not refill when bottle cooled, so you pay to get a 200 / 300 BAR fill, but when you get home and the bottle have cooled you only have 180 / 280 BAR in it, and that’s infuriating.
I would hate to fill little rifle bottle with a little compressor, that would be infuriating too CUZ when i shoot i do so for at least 4 hours strait, and in summer +8 hours are not unheard of,,,,,,, that will be a lot of fills from a big bottle or a little compressor, so i connect to my big bottle and dont look back for hours on hed,,,,, which i can as i shoot from a bench so everything is right there.
So if you have a dive shop or fire department or paintball club that can handle your big bottle filling needs, and you do not shoot a air guzzling big caliber or super much, i would also say get a big bottle, and a 5 foot long hose so you can connect permanently to the rifle instead of filling little rifle tank all the time.
I in general shoot at least 1 time a week, in summer 2 days in a row is not unheard off, so that be around 2000 .177 shots in one outing.
A 12 L bottle shooting tethered will have enough air for several of outings like that, shooting .22 and not necessary the heaviest of ammo all the time, you can pull that off too.
So the big ? is, what is the price of your free time, is it low enough that you can spend a little of that one time every month to go to the shop to get you big bottle filled.
Of course if you are a fill / walk and shoot kind of guy, well then you can not shoot tethered to a big bottle, but you can still fill from one, just have to be mindful its pressure of course drop from every fill, but also many fills in a 12 L bottle even if you have to stay above a fairly high pressure to still have a decent shot count on every rifle refill.
