SL58,
No question that a finely crowned muzzle as pictured is desirable for fine accuracy. But it seems your problem is more severe. Being an early re-pac yours seems to share the same symptoms as my 25cal had; accurate shots but WAY off center. So bad that the scopes just ran out of adjustments. Using thin matchbook cardboard shims under both the rings to scope/ and mounts to receiver to position the scope I was at least able to get on target with the factory set up. Knowing this still was wrong I bought the metal replacement piccatiny rail aftermarket scope base mount for the receiver and it solved my problem. They were offered both on EBay and from Pyramid Air for $40, Uhg! But it worked and now I have full adjustment abilities with my scope like with my other rifles.
I understand the other projects taking priorities and becoming sour on the Avenger, but I have to tell you how pleased I am that I didn’t just put mine away. As it shoots now with mods it equals or surpasses all of my other pcp’s at long range.