1.5" is fine.
I know, I know, everyone shoots sub-1" groups with surplus ammo at 100 yards with these rifles (sure they do
) but the rifle itself isn't expected to do any better than put all it's bullets in a 4cm circle at 25 meters. That's rifle + arsenal/factory ammo + shooter. You're doing this.
All hits inside a 4cm circle at 25 meters will hit mansized targets at 300 meters.
The practrical limit of many M16/AR15 rifles and factory ammo, even with trained firers is 3cm at 25 meters. With match ammo, off the bench with a scope you'll shoot better, but for now try to get some of the silhouette targets from
communities.msn.com/TheMarylandAR15ShootersSite and see if you can tighten the groups up a bit. I believe they have rescaled them for 25 yards and 15 yards.
They have scaled targets so you can shoot those 300 meter targets.
Don't be afaid to try a different ammo type. The Lake City M193 Ball looks very nice and produces very tight groups off the bench.
-- Chuck