When you have a crash that creates a crash dump, it usually goes in a folder within the game's installation folder; in Steam this would be:
C:\Program Files (x86)\Steam\steamapps\common\BATTLETECH
You will also need to attach the game's log file:
C:\Users\YourUserName\AppData\LocalLow\Harebrained Schemes\BATTLETECH\output_log.txt
To see the AppData folder you'll need to enable View Hidden Items in File Explorer.