The smallest single group ever shot in competition at 300 yards was a .149" shot by Gary O'Cock. The smallest 5-group AGGREGATE shot at 300 yards is .1518" shot by Bart Sauter who is the maker of Bart's bullets. This .1518" aggregate is NOT actual group size! Bart's average group size at 300 yards was .455". An AGGREGATE is the average group size of five-5 shot groups, and is in MOA. So for example during an aggregate at a match you have 5 groups (5 shots in each group) of .650", .725", .500", .820", and .740" measured using a 6" Caliper at 300 yards. The target scorer will add these measurements to get 3.435". Then divide 3.435" by 5 to get the average group measurement which is .687". Then divide by 3 (because this is 300 yards) to get your aggregate which is .2290" MOA. Groups measured in BR competion are all measured to the thousandth (.001") whereas aggregates are always recorded to the ten-thousandth (.0001"). The best Benchrest shooters in the world using a modern top-of-the-line BR rifle chambered in 6PPC are usually able to shoot aggregates of around .2500" at 300 yards on a regular basis. That is 1/4 MOA. World Record aggregates at 300 yards such as Bart Sauter's .1518" are incredible but are extremely rare. And world record GROUPS such as Gary O'Cock's .149" at 300 yards are even more rare and involve a lot of luck. To shoot aggregates and groups this small a shooter has to have a GREAT rifle that is in tune and has to be on top of his game. With my top-of-the-line BR rifle using windflags, handmade bullets by Bart Sauter, a 36X scope, solid sandbag rests, Lapua brass, I am occasionally able to shoot a single group under .100" at 100 yards. My smallest 200 yard group is .240". But my 100 yard aggregates are usually around .2500" if the rifle is shooting well. The true test of a rifle's accuracy is NOT the smallest single group a rifle has shot, but the average or aggregate of 5-five shot groups.
The guy you talked to at that gun show is full of ****. If he was able to shoot groups like he told you at 300 yards, his aggregate would be between .0833" and .1166"! The existing WORLD RECORD is .1518" shot by one of the best shooters in the world using a 10.5 lb. Benchrest rifle using the finest custom actions and barrels available, chambered in the most accurate caliber in the world the 6PPC. There is NO way in HELL he could shoot those kind of groups outdoors using a .243 Winchester case necked down to .223 and I would bet he NEVER uses windflags. Even a rail-gun would not be able to shoot those groups consistently in an underground tunnel unless it was exceptional and was in perfect tune!
If you talk to that guy again tell him to show up at the NBRSA Long Range nationals next year (200 and 300 yards) and completely KILL the best BR shooters in the world with his .250" and .350" groups at 300 yards.
Jake Hayes