If he's a first time hunter, I recommend the full flush mount choke that the gun comes with.
My son has shot the 510 Mini for many years with an FFII on top, and shoots the Federal Heviweight 3-1.5-7's.
This combination puts 193 in the 10" circle at 30 yards, and the pattern is very even.
Just some food for thought until he gets more experience.
If he's been shooting for some time, the SSX is a fine choke.