The SAK is Fine and the Zet Z is brilliant, just exactly what do you expect...you are not talking about a .22LR SUB Sonic!
With regards ammo, what do you want to aim it at?
CCI Maxi Mag is 40g and a TARGET round and should not be first choice for fox!
Hi here are a few to concider for close range fox
Hornaday 30grn V-MAX Magnum Balistic tips
CCI .22 Magnum 30grn V-Max Poly tips
Remington 33grn V-Max Balistic tips
arcpest