Recently brought home a very lightly used M&P10 .308 with 18" barrel and M4 style handguard. Looking to turn this into an outdoor range plinker that I'll use mostly from shorter distances (100-300 yards) and occasionally out to 500 yards. Am intrigued by the cylindrical look of the 15" free float handguard from Apex Machining. Anybody have experience with their product? And finally the dreaded optic question.....given the use and $500-$600 budget, any thoughts or recommendations? My first venture into magnified optics so I'm starting from scratch.