In the use of precision long guns, there is a continuous effort to improve accuracy and precision, in other words the accuracy of the weapons. These characteristics of the weapons are determined by the consistency of the whole “weapon system”. In this article, we will explore the application of a method that offers a relatively low-cost development opportunity for sport shooters and shooters who use manual ammunition assembly (reloading), which can greatly improve the accuracy of the weapon. The method described in this article adjusts the time the projectile spends in the barrel to achieve a pre-calculated state of barrel deflection and vibration. To do this, it varies the ammunition assembly parameters (load size, seating depth, neck extraction force, etc.) to tune the internal ballistic processes in the weapon. The procedure is referred to in the literature as “Optimal Barrel Time” (OBT).