there's probably 100 different ways you could rig a rail ontop of that receiver. It's only a 22 so it's not like you're going to have massive recoil to contend with. I guess they wanted to go with an "authentic" look
looking at it again, i'm sure you could rig one of those cheap ar-15 handguard rails to the barrel shroud without any modifications
looking at it again, i'm sure you could rig one of those cheap ar-15 handguard rails to the barrel shroud without any modifications