There is no such thing as a BEST call. My favorite most producing call probably isn't the BEST for someone else. There are hundreds of open reed and enclosed reed calls on the market and most everyone one of them will work to call predators, IF the user puts the right emotion into the call.
If you've no idea what sounds you're needing to mimic to call predators, I'd also suggest buying a calling video, or two, and watch and listen to how it's done, then go from there.
I'd suggest starting with enlcosed reed calls, as there are simple but effective.
your elephant gun will do fine. I'd take a wild guess and say if and when you connect on a coyote, it'll be DRT!