Optimum 6.5 Grendel bullet weights

[JASmith]

...From a 10.5" barrel, MV would likely be no more than ~2175 fps. Minimum expansion velocity of the 120gr TSX is 1800 fps...

The 2175 figure might be on the high side unless the powder is selected for optimal performance in the short barrel. A load using TAC to get 2420 from a 24" barrel would be likely to be somewhere between 2025 and 2125 ft/sec per the Ammoguide.com velocity estimator.

Going lighter means you give up penetration depth and barrier defeat. Bottom line, it depends on what effects you want to emphasize.