Anything you shoot out of there will drop a coyote quick so it depends on what the rifle likes the best.
If he starts with lighter bullets I would try out some Hodgdon 4350 powder, if he starts out with bullets in the 123gr+ range I would start out with some Hodgdon 4831sc powder. If it's a 1-8 twist I would try some 140gr bullets, if it's a 1-9" I would try some 123-130gr bullets. 1-10 twist go even lighter.
And I have had great luck with the CCI BR2 primers.