Steve
What I shoot is called group shooting. We shoot 5---five shot groups which is called an "aggregate". In a typical "two gun" we usually shoot an aggregate in Light Varmit Class (10.5#max weight of gun) and Heavy Varmit (13.5# max weight of gun)I shoot the 10.5# gun in both classes. We shoot an aggregate at 100 yards for each gun and another aggregate at 200 yards for each gun. So a total of 4 aggregates are shot at a typical two gun weekend event for a total of 100 record shots.
Groups are measured by a magnified lighted reticle to one thousandth. A calculation is made to get to the 4th number .0000(tenth of a thousandth) For instance at 100 yards if your 5 groups for the aggregate measure .181 .195 .223 .250. .295 you add those up to come up with a total of 1.144 divided by the 5 groups and have shot a .2288 aggregate. If they did not go to the 4th number there would be a lot of ties.
When shooting a 5 shot group it can be anywhere on the top target as long as it is inside the thin black square line. The object is to put 5 shots into the same hole, not necessarily to hit the bull. When measuring a group they measure the size of the group from outside to outside and deduct the size of the bullet, .243 in most instances to come up with the size of the group.
Not only do you have to factor in the wind and hold accordingly, you have to keep your gun in tune. A winning bullet seating depth is most always within .002 of optimum. If you are off 2 or 3 thousands from optimum then you are out of tune and will not score well. Also a powder change of .3 of a grain will effect winning accuracy. Usually if you have the correct seating depth it will stay the same all day or even all weekend. The trick is to stay on top of your powder charge, dope the wind and read the wind flags you have out between you and the target, and start your group at the right time. The wind usually has patterns and you try to shoot when the wind is not blowing hard, a tough feat some days. You don't see very many one's such as mine shot at 200 yards at matches. You can get what they call a "screamer patch" for a group smaller than
.250@200 yd and
.099@100 yds. Last year I shot 2 screamers at 100 yds. One was a .081 and the smallest I have ever shot.