You might find some minor differences between grocery store battery brands. But they're all the same chemistry and construction, so they all perform very similarly. Stick with alkalines tho, the Heavy Duty carbon batteries are total crap.
The RapidStrike is a notorious battery sucker. And C batteries have the worst current to weight ratio, Hasbro really should have used D's in the RapidStrike. Who cares if it weighs 4 pounds 😉
BTW, the RapidStrike is also one of the easiest blasters to convert to IMRs or 2S LiPo. All it involves is minor modifications to the battery tray. I've made a 2S tray that I can use interchangeably in multiple RapidStrikes. It lasts all day on one charge.