The wind(flags) are your friend...
If you don't have flags, invest in a good set and learn to read them. There are times when bc matters in short range but they are few, to be honest. For starters, the higher bc bullet and/or load has to be as accurate as the other load. If not, the cost will out weigh the benefits most of the time, inside of about 300 yards. This is with flags and reasonable flag reading skills. There's simply not much that is more important to shooting well than reading the wind well.
That said, your 222 is stretching it's legs pretty far at 300 and is a bit beyond it's ideal range. If you're dead set on shooting your 222 at that distance, you simply have to overcome the advantage that the other calibers have on you by out shooting them. This really translates to reading the wind better than they do...by a good bit. If flags are allowed, by all means, get some good ones and practice, practice, practice with them and use them at the matches. If not, then yes, I'd most certainly look into a better caliber for that yardage, that does better in the wind.
I just won a 200 yard match in some really brutal conditions where I did actually switch barrels between 100 and 200 yards. I went to a 6 Grendel 12 twist, shooting 80's at 3,300fps. I completely stunk it up at 100 with my 30 and won the 200. I have no doubt that in those conditions, the better bc did carry me. But, that cartridge shoots exceptionally well. I don't think it leaves much on the table in terms of outright accuracy vs my 30 barrel that has won at least one yardage in 3 of it's 4 prior matches and was a reticle away from tying a record at last year's UBR Nats. It's a real good shooting barrel. The Grendel is close if not just as accurate but with a much better bc. Roughly .450 vs .300 and faster too. I'm starting to like it! Lol!
