hi guys , i'm new to this forum . i recently purchased a HANDI-RIFLE (survial) IN .308 . IT HAS THE HEAVY BARREL AND THUMB HOLE STOCK . I LOVE THIS LITTLE GUN , BUT THE GROUPS ARE A LITTLE LARGE AT 100 YRDS , 5 to 6 inches. i have a set of WARNE maxima steel rings and a BUSHNELL 1.5X4.5X20 SHOTGUN SCOPE INSTALLED . HOW CAN I TIGHTEN UP THESE GROUPS?