Mike, depending on the event and the "sanctioning body" they are the ones who dictate gun weight.(in some cases or the actual range / club holding the events).
A lot of ELR matches have a 40 Lb. gun weight limit (which includes the bi-pod if used).
King of 2 Mile I believe is 40 pounds.
Up in Montana the Elite Long Range Competition (
Home | Elite Long Range Competition (elitelrc.com) has at least 2 classes (use to be 3) and is a new & growing organization run by some of the 1000 yard BR shooters.
Has Unlimited (shoot from a bench off a rest OR a Bi-pod, or prone position on the ground with either a rest or bi-pod). And an ELR class - The web-site should have more info.
I own & shoot everything from a 50 BMG Improved on down. - The 338 Lapua Improved has done well @ 2000 yds for a bunch of shooters. - Beyond 2500 yards is where I'd say the 375 Chey-Tac's, 416's & 50's have a nitch. - I don't claim to be an expert, I'm more of a student at this point. - I've got a good deal of good hardware, but need to gain more experience.
Also there is ELR Central (
Home - ELR Central) and they have an "events page".
Here's a link to some locations (
ELR Locations - ELR Central)
Hope this helps in answering some of your questions. - ELR covers a LOT of ground !! -
(Oh and you'll need to plan on spending a fair amount of cash especially if your going to build one of the really big boomers).