JBM Ballistics also has an on-line program based on the same formula, except for including a place to enter the length of plastic tips.
The guy who developed the formula Berger uses, Don Miller, eventually came to the conclusion that plastic tips are so light they don't affect stability much, so their length shouldn't be included when calculating stability. This is why the Berger formula suggests that 40-grain Hornady .204 V-Maxes won't even come close to stabilizing in the standard 1-12 twist, when anybody who's used them knows that's not so.
When using the Berger program with plastic-tipped bullets, I subtract 3/4 of the length of the tip from the bullet's overall length, which so far has worked pretty well--and comes close to the results from the JBM program.
