Are you trying to run this sub 12 ft lbs or is it FAC?
Set up wise, i am running a TTR1 with a 14 inch barrel, reg set at 1500psi not the manufactures recommended pressure which is higher, (.177) and i can achieve way over 100+ shots before i even hit the 100 bar reg pressure even from a 280cc bottle.
Rapids are really easy to set up right, but a few more details, i.e model, reg'd or un regged, internal set up etc and it can be run correctly in no time at all.
Actually just noticed you are in Cardiff, if you fancy a trip to Llanelli at any point, i can set it up with you if that helps?
Theoben TTR1 .177, Steven B Blue/Grey Laminate Stock, Nutshot Mod, Falcon Menace 10x42 B20 Ret