Limited Weapons
I would not use the Isis CB5 unless you have a specific need for it. Limited weapons are less efficient than their unlimited counterparts, not only because you consistently pay markup every time you repurchase, but you fail to retain your tiers gained (even if they do tier much faster).
Whereas, with a UL weapon, your tier, and your investment in a Tier, is a capital asset (technically). Its just a matter of finding which chip will benefit you rather than cost you more (if eco hunting is your aim).
I will tell you right now, the eco enhancer is not the most economic enhancer in the game, especially not for low level weapons. (In fact, you will pay more for the eco enhancer than it will ever save you in ammo costs). However, I have found one enhancer that does significant justice for the Opalo, especially with a101.
Source: I've used one Opalo, the same Opalo, in my hunting set for around 2 years.