In .177 I have had good luck with the winchester round nose and the Tomahawk's both 7.6gr the pro magnum .177 shot crappy in everthing I tried these are all made by Gamo
Just get an idustrial Nitrogen regulator rated for 4500 psi from the local welding supply co Harris , Victor ,Smith and many more probably in the 3-4 hundred$ range but shop around find out who repairs reg's in your area might find deal on used
Thats the one I have it's been going for almost 2 years no auto anything and I only feed my compressors Nitrogen . Do Not use Royal Purple I use chemlube 751 also hear good things about Rarius?? (spelling)