Crossbow bolt

A bolt consists of 4 main parts;

• Shaft: It is main body of the bolt in which other parts of the bolt are attached. Shaft is normally made of carbon or aluminum and are very light weight (so they can cover maximum distance), they don't bend or splint. However sometimes both aluminum and carbon are used. Shafts come with varying degrees of stiffness; that stiffness is referred to as the “spine” of the bolt. The more resistant to bending an arrow is, the more “spine” it is said to have. The weight of a shaft is in grains. When you purchase a bolt the manufacture either mentions the total weight in grains or can simply provide GPI value. If only GPI value is provided you can calculate the total weight of shaft by multiplying the GPI value with length of shaft in inches.
• Fletching: Fletching also refereed to as vanes are the wings that are located at the end of the shaft just before the nock. It is made of plastic or other soft materials. They are of great use and serves 3 main purpose; to stabilize the trajectory of the bolt mid-flight, help it keep going in the proper direction, and to prevent it from pitching or swaying to the left or right. Fletching also cause the bolt to spin around its axis during the flight. There is no rule or formula for length of fletching, generally the longer the shaft is the longer fletching is and vice versa.
• Broadhead: Broadhead is the head of the bolt or arrow that is sharpened so that it can penetrate in the targets. There are different kinds of broadheads that includes, fixed, removable and expandable.
• Nock: A nock is a small object that is attached to the end of the shaft. It helps to keep the bolt in place. Nocks are made of either plastic or aluminum.

There is not any hard and fast rule of bolt sizing. Generally, the bolts are of 15 to 22 inches long but the standard length is 20 inches. [3] Experts recommend longer bolts [4] but they have certain advantages and disadvantages as well.

The weight of bolt can have a serious effect on the range of your bolt. The bolt's total weight includes the bolt's weight, nock, insert, vanes, and broadhead or field point. Almost all bolt manufacturers will list how many grains each shaft weighs or how many grains are in each inch of the shaft. Let's assume; your bolt is 15 grains per inch and has a length of 20-inches, then multiply 15 x 20 to find your bolt's weight. Now add the weight of the nock, shaft, fletchings, and tip. A more massive bolt, at least 400 grains, not including the head, will have better downrange energy and offer better penetration. Keep in mind that even though a bolt will leave the rail quickly, a more massive bolt will soon lose power as it travels. A bolt on the lighter end of the manufacturer's instructions will fly quicker and give the shooter a long-range but might not get the wanted penetration.