I shoot score at my local club - Austin Rifle Club - and use a 6BR. I can hold my own against all those 30s and won High Score for 2015 with my 6BR. My setup is a Shilen DGV, Shilen barrel/nut, B&A trigger, McMillan Edge LV, and a Sightron 10-50 scope. I went with the DGV because I wanted to be able to change barrels without needing a gunsmith, and I have done this 3 times now. It's really pretty easy:
1. Remove action from stock and firing pin from bolt.
2. Place GO gage in chamber
3. Lightly snug the barrel down on the GO gage. The bolt should close on the GO gage.
4. Remove the GO gage and insert the NO GO gage. The bolt should close about 1/3 to 1/2 of the way.
5. Give the barrel nut wrench a firm tap with your hand.
6. Remove NO GO and insert GO gage. Bolt should close easily again. Give the barrel nut wrench a much firmer rap again and test the GO gage again.
7. Finish up with the NO GO and check for 1/3 to 1/2 closure. Reassemble the action/stock and go shooting!
Having said all that, if I were going to try my hand at national matches, I'm not sure I would stick with the Shilen, but would certainly give it a go at the beginning. As suggested, though, a used BR rifle with one of the actions mentioned can be had for a lot less than I put into my DGV!
Dennis