realistically if he wants to be competitive a 5p size group is not going to cut it, the bull size is only slightly bigger than the pellet, take into account windage on a low power rifle and the scores will be well down. At 50 - well good luck! Stick with a 16joule for 25-50 if you want to be competitive. If you only do 25 then the lower power will do the job but bear in mind some comps/clubs are outdoors and you will definitely be at a disadvantage. I'm struggling to think of anyone i've seen using a 10m rifle at 50m competitively against 12joule and FAC .22 which generally shoot in the same class as each other. Someone i dare say will prove me wrong!