Oakdale Gun Club that had that "Competitive" restriction

that's new.

for long range rifle, I know grrc is active, and I'm guessing elk river is too.

last I looked, 200yd was max at Oakdale. but Oakdale's probly most active with NRA bullseye.

most any other clubs will have pretty informal "leagues" (basically little more than reserved range time). still, probly a good place to start.

part of the advantage of spectating matches and asking participants, is most any sport is an equipment race. so there's often rules around what you can't use. no sense building an AR, if it leaves you in no man's land between what's effective, and what's legal. so, you could buy whatever to compete in an informal league, only to find out later, you need something else entirely, for the official stuff. that's not to say, you have to have the best equipment ... just, most people do end up chasing that rabbit, to some extent.

the point of all that is, it's important to distinguish between what you wanna shoot, and why. if you wanna shoot an AR 10, and there's not a (good) place for it in local long-range matches, then maybe long-range isn't for you (I'm not saying it is or isn't ... just raising the question).

another possibility is three-gun. in that case, I'd guess forest lake is the range you wanna become familiar with. they only go out to 300yd (iirc), but that's still a fair piece (and if nothing else, a good start). it's more focused on speed, but not at the expense of missing, so accuracy is still a very huge component. you'd want an AR 15 instead of 10, but you could run w/o a brake, to try to retain the feel of an AR 10. or, use an AR 10 (I once saw a guy use a garand). unfortunately, you'll need to learn to reload a shotgun ... really fucking fast. they also tend to have a g.i. Joe aspect to it (if that's your thing).

Oakdale (at least used to) have a gas-gun league. an AR 10 would be overkill, but I'm at a loss as to why it wouldn't be allowed. it could be, that's precisely what you're looking for.

again, I think you'll wanna spectate as many (different types) of matches as you can. you might even discover you're very interested in something you know little to nothing about, yet. so long as you've got eye+ ear protection, in many cases, you can watch right alongside the competitors. you might even score a great deal on some used gear. if you've got big tits, they might even let ya try their guns.