I would be hesitant to take advice from the likes of me, too. Haven't shot in a big match in quite a while. I'm still in awe of the guys who can shoot the teen agg. I'm sure they put in lots of practice. And that's just one of the reasons they can consistently shoot small. Pretty sure that an average barrel and average bullets aren't the ticket .
Somebody who has a tunnel and has done lots of testing might have the best recipe for shooting zeros.After you have the right neck clearance, I'm guessing you still need good brass, consistent neck tension, the right amount of powder, a scope that is solid, good rests, and bench manners. And a target that doesn't move.
I take one thing back.. every match is a big match. There are really good shooters every match that I attend. And the people who put on a match do a lot of work to make a match happen. So if you happen to be on top , you had a good day.