I’m confused when it comes to purchasing bolts. I’ve seen it is recommended that total arrow weight be 400 grains. Is that based on a certain bow speed range? I made my first crossbow purchase for my son with the Barnett Terrain XT, rated at 330 FPS. It came with 2 20” Barnett Headhunter arrows and I’m looking to replace them and add a few more. I’ve looked at several bolt types at Local stores, but most of the boxes don’t post an arrow weight. What would be a good rule for hunting use for this bow?