some bow manufacturers like PSE/Archery Research
Require arrows to weigh 6 grains per pound of draw weight so if your bows peak drawweight is 70 they want you to shoot a 429 grain arrow

most other companys require to shoot at least 5 grains per pound

only 2 companys will warrant their bow to shoot less than 5 grains per pound, High Country Archery and Archery Pro LLC.