I believe it's better to go with a smaller caliber bullet with enough powder to do a good job.
My son and daughters all used a 40 caliber bullet with 90 gr of powder to start with.
I recommend the 200 gr 40 caliber Shock Wave, the 200gr Lehigh and the 200gr XTP with a practice load of 80 gr and a hunting load of 90gr. in a 50 /40 sabot.