Science!
The effect of bolt bounce is due to the BCG slamming into the barrel extension and then partially coming ("bouncing") out of battery and then settling back into battery again. All else being equal, a heavier barrel recoils with more energy, thus requiring a heavier buffer to counteract that recoil.
For example, the H2 buffer was created / implemented specifically for the the M4A1 SOCOM carbine, which has a much heavier barrel than the standard M4, to ensure reliable full-auto fire. In that case, the change in buffer weight was solely due to the heavier mass of the barrel. It wasn't a dwell-time issue, as there were no changes in the gas system or barrel length between the SOCOM and standard barrels. :handgestures-thumbup: