Unless you just want a new gun, my advice is going to be a little different.
I say use what you've got for a while. Learn what calling coyotes is all about. Learn their habits, how to set up your stands for success, and how to call and out-smart them.
Later, when you've learned all the above, you'll know what cartridge to get to best match your hunting style and technique(s). I've seen a lot of people go buy a "varmint" rifle that's way to heavy, with too long of a barrel for a good calling rifle. They get out there and have coyotes almost in their laps, and that heavy, long barreled rifle is like swinging a full-length stick of rebar around in tight cover.
Seriously, learn what works, and learn what doesn't before you decide what will best work for you.
Daryl