I shot a lot of competition, same BHFS-L class as ArthurP, and I've seen some amazing shooters out there. I couldn't do it all the time, but many times on the indoor range, put all five arrows in the x-ring. There were some shooters that did it a lot more regularly than me. Especially with releases, scopes, 10 yard long stabilizers, etc. And some of the top field (notice I didn't say 3-D) archers can easily shoot 3" groups out to 40-50 yards. Hell, I won a novelty shoot one time shooting 10 eggs in a row. They were dangling by a string at 40 yards.

So it's definately possible.