Player's Option Weapon Mastery

[SaurOps]

I never really got to use or test this out, but it was something I was wondering about. The ultimate end of weapon specialization in the Combat & Tactics book was Grand Mastery, which increased your weapon's damage die/dice size by one, among other benefits. While it's cheesy and the reasons for why it did slightly more damage (if somewhat more infrequently) than a typical two-hander suspect, the no-daichi did 1d20 damage to large and greater size critters, so did this mean that you rolled 1d100 for damage if you were a grand master of the no-daichi and fighting a larger opponent?

[Magua]

I have a d30 in my bag of dice.

[SaurOps]

I have a d30 in my bag of dice.

Which would be a sensible call to make, but I was asking about the RAW intentions. I don't think that they used a d30 for much in 2e.