When lifting weights, i currently lift 12 times for 3 reps but i have heard that is what bodybuilders do and isnt the most fuctional way to bulk. Is it true that this is not the best for boxing? If it is, what are better rep ranges to bulk for boxing.
There is no such thing as functional muscle. That's broscience/pseudoscience at its finest. You will never have a heavy load on your back and have to squat it in every day life. You will never be lying down on your back and have to push something up. The only lifts that have any sort of relevance in every day life are overhead press and deadlift. From the dawn of man we have been lifting heavy **** over our heads or picking heavy **** up off of the ground. However the carryover is minimal because an object that you pick up isn't leveraged like a barbell is and won't always be easy to grip. For boxing I don't find that lifting weights is that good. For adding bulk they are, which is why I use them, but for boxing they shorten the muscle whether or not people want to admit it or not. I have personal experience with this also Riddick Bowe can back me up on it too. If you want to get strength that has good carryover to boxing then do manual labor. I have always found that that builds the most realistic strength.
Lifting weights does not add mass to your body, consuming a surplus of calories does. If you're lifting as a boxer your goal should be increasing overall power, muscle would come with a surplus. Check out something like Westside for Skinny ******* 3 for a generic athlete training program.
Lifting weights in certain rep ranges helps increase muscular size. That's why bodybuilders work in the 6-12 range whereas endurance athletes work in the 20+ rep range. Weightlifting and eating big will build muscle regardless of rep range like you said but other rep ranges work better for increasing size.