BG kills have been introduced into tapering just like wacking has.  This has been done so that the BG cap does not have to be adjusted.

The top 10 guns in the game that are above 650 wack after max are set to taper like this:
#01 50% (From 650-1000) (25% From 1000-1350) (10% From 1350+)
#02 55% (From 650-1000) (30% From 1000-1350) (15% From 1350+)
#03 60% (From 650-1000) (35% From 1000-1350) (20% From 1350+)
#04 65% (From 650-1000) (40% From 1000-1350) (25% From 1350+)
#05 70% (From 650-1000) (45% From 1000-1350) (30% From 1350+)
#06 75% (From 650-1000) (50% From 1000-1350) (35% From 1350+)
#07 80% (From 650-1000) (55% From 1000-1350) (40% From 1350+)
#08 85% (From 650-1000) (60% From 1000-1350) (45% From 1350+)
#09 90% (From 650-1000) (65% From 1000-1350) (50% From 1350+)
#10 95% (From 650-1000) (70% From 1000-1350) (55% From 1350+)
#11+ Normal