I have been working with a paintball tank and reg and at 1350-1400 I can get 775 out of an 18 inch bbl with 14g wc pellet.
The paintball reg has a lp burst disk of 1500, blew that yesterday, so I put in a 3000 that I had laying around. Maybe I need to crank it up some more……. 🙄 better talk to Eric (owns that gun) before I break something.
That tank and reg does look very similar to what I am working with.