"Construction, not weight."
Yup. Although, in general, a thirty-caliber 180 is of heavier construction than a 150. That showed in the crater depth on steel at my 500 yard range.
An example from my own experience: The Sierra 150-grain SPBT will blow up if the impact velocity is at or above 3,000 ft/sec. The flat-base will not; it's of slightly heavier construction.
You're from BATFE? Come right in! I use all your fine products!