The factory tupperware stocks are pretty lousy at best. Boyd's makes some nice laminated wood stocks that work very well. The factory trigger could also use an upgrade,and there are several to choose from.
Both of these upgrades will vastly improve the shooting ability of the rifle. As others have said,the sporter contour barrel's are designed for hunting,and most don't shoot very well after they heat up.
If you use a good solid front/back shooting rest,your groups will probably improve a lot if you let the barrel cool 5 minutes between shots.
Some rifles are very picky about what they like to shoot,so don't get discouraged when it doesn't shoot a certain type or brand well. I spend a lot of range time finding out what each of my rifles like to shoot,and I strictly handload for everything I shoot.
Try some 150 or 165gr hunting bullets-Soft point or Ballistic tips,and it may shoot a lot better than the match grade stuff.