Traditionally, no, you can't. That is unless you have the Crossbow expert feat. This feat allows you to ignore the loading property on your crossbow and make multiple attacks with it in the same term - e.g., if you're a fighter and have multiple attacks, congratulations, you can now attack with your heavy crossbow as many times as you want (so long as you're proficient with them). As an added bonus with this feat, you can ignore the ranged requirement and don't make your attacks at a disadvantage when your enemy is within five feet of you.