On January 1, 2012, all baseball bats used in NFHS play must pass the new BBCOR Bat Standard. The -3 weight limit, 2 5/8" barrel, and MOI (moment-of-inertia) minimum limits will remain unchanged.
BBCOR stands for "bat-ball coefficient of restitution," which measures how efficiently the ball rebounds off the bat taking into account the properties of the bat and the ball. This new bat standard replaces the previous BESR standard and is designed to achieve wood-like performance in non-wood bats.
There will be no opportunity for "grandfathering" of old BESR bats.
The BBCOR limit (0.50) is equivalent to slightly higher than the best-performing wood bats. Most of the wood bats tested in the mid .480s on the BBCOR. A few of the highest-performing wood bats tested in the low .490s. The sweet spot on the non-wood bats will be larger than wood bats.
The requirements to pass BBCOR will make a typical aluminum bat MOI feel like using a 1" longer bat (but at the same length). For alloy bats to pass the BBCOR, the barrel walls must be thickened. A thicker wall will make a bat swing heavier. Composite bats will feel lighter because there are other ways to control performance than just by thickening the wall. Composite bats will also have a larger sweet spot.