To touch a circle of .500 diameter with 30 caliber bullets you need a group of .8 ( .5 +.3) perfectly centered.
At the CBA nationals in Charlotte NC, this year, 2004, the 100 yard 5 shot group match of 4 groups per shooter, had an AVERAGE group size of .874 for all categories. The Production rifle average was 1.042.
If you can AVERAGE an honest inch for five shot groups at 100 yards, you'll beat the average shooter in production class, and on a good or lucky day, you'll be well up there in the rankings.
The plain base bullet class = single shot old time rifle shooters, there were four of them, averaged .848 for four 5 shot groups each. These without heat treating bullets, at slower velocities, without gas checks even. Lotsa bucks in the guns maybe, but this shows that careful loading with right components can do the job without high tech high velocity loading.
There were 5 aggregates = averages under .500 inch out of 39 shooters. One in HEAVY class, one in plain base bullet class, and 3 in Unrestricted = rail gun class. It's hard and unlikely to shoot under .5" averages. There's a lot of wind doping and slick luck involved.
Go slow, cast good bullets, keep good records and read all you can find.
It ain't hard, and it ain't complicated.
joe b.