First steps are to make sure his rifle is clean and properly lubricated, AND that the take down screw is snug but not overly tight, with both halves of the receiver fully seated.
If you can see a "step" where the receivers join, the rifle isn't properly assembled and will often mis-feed. This usually means the screw isn't properly tightened.
If it is the ammo, just try a box of several better brands before buying a lot of it.
What works in my Marlin may not work in his and vise versa, so it's impossible to really recommend a brand or type of ammo.