Accurizing is the process of improving the accuracy and precision of a gun (firearm or airgun). For firearms, accuracy is the ability to hit exactly what one is aiming at, and precision is the ability to hit the same place over and over again in a repeatable fashion. Both are the goals of accurizing, which generally concentrates on four different areas: Usability: Enhancements that give the shooter a firmer and more controlled hold on the firearm, as well as a more consistent trigger pull. Better design ergonomics is often employed, such as adjustable buttstocks and grips with more vertical angles that are natural to the human hand and wrist (e.g. pistol grip). Spirit levels are often mounted to prevent canting, which can vary the points of impact. Weapon mounts such as bipods, monopods, benchrests, shooting sticks or simply sandbags can provide a more stable and relaxed platform for the shooter, and devices such as muzzle brakes or compensators can also be used to help counter the muzzle rise from recoil and re-establish aim faster and more precisely for repeated firing. The use of suitable slings can also help shooters to stabilize their aim when shooting off-hand while standing or squatting. Tolerances: Parts that better fit together will shift less, or shift more consistently, under recoil. Rifle bedding is one of the most common practices of such accurizing procedure. Adequate screw torque setting between the action and the stock is also important for the overall rigidity of the system. Some companies, such as Savage Arms, have even introduced features like floating bolt head to provide better bolt-breech engagement for more adequate breech seal and headspacing. Harmonics: The act of firing a gun generates a rapid pressure increase within the barrel bore, causing the barrel to resonate and vibrate in a rope-like fashion. The resultant harmonic oscillations of the barrel affect the terminal phase of the projectile's internal ballistics and in turn the initial status of its external ballistics, and therefore need to be minimized or tuned to limit their effects on accuracy. Generally the harmonic effects are proportional to the square of the barrel length, and so are generally only of concern in long guns such as rifles but not handguns. Some external accessories, called tuners or de-resonators, can also be mounted onto the barrel to alter the harmonic wave pattern so that the node is shifted as near to the