Having the correct arrow or bolt is vital, weather it comes to compound bows or traditional one, crossbows, modern or not. Is seems to be accepted that a bolt with a weight of about 2 grams (30.8 grains) per pound of prod draw weight is a good place to start. Bolts which are to light can cause damage to the prod and the bow string, often breaking the string at the knocks, light bolts don’t absorb the energy from the prod efficiently ether, causing your crossbow to sound loud and not imparting the kinetic energy and momentum to the projectile which it is capable of. You can go the other way , with a bolt which is to heavy, giving slow flight and a massive trajectory, neither of which are good for hunting. A slow bolt speed gives the target time to move, causing a miss all together, or worse, wounding it.
The idea is to find the middle ground, good speed, but with the weight to quieten the crossbow, and to help keep the bolt on track in windy conditions.
The bolts which i build are made from Balu , a heavy wood, stable and strait.It take a very smooth Finnish and i am yet to break one, even shooting into a 50mm board of Meranti from 20m. If im looking for more weight, i insert one into the shaft before gluing on the point or broad head, this gives the added benefit of increasing the forward of center of the bolt.( distance from the back of the bolt to where it balances on a knife edge) My current hunting bolts are at 17% FOC, and i get great flight, even with my 160 grain ace broad-heads. 4 or 5in feathers are the only way to go when it comes to fetching.
When building bolts, i treat them the same as my crossbows, only accepting the finest strait shafts, and finishing them with the same quality’s, with either field points or broadheads as required.