The paper deals with an adaptation of the standard interior ballistics model for the case of amphibious rifle shooting ammunition under water. The adapted mathematical model was validated and experimentally verified using the 5.56 mm underwater projectile shot from the 5.56 mm amphibious rifle. The dependence of the underwater interior ballistic processes on the powder mass was investigated. The results of theoretical mathematic model solution correspond very well with experiment. The described mathematical model and the dependence of the underwater interior ballistic processes on the powder mass can be a reference for designers in the design process of the underwater ammunition or underwater rifle.

Designed for amphibious combat forces, the amphibious rifle is a revolutionary new kind of weapon. This firearm's design and the determination of the effect of shooting on the shooter are both dependent on the development of the underwater muzzle blast. In this work, an experiment to evaluate the muzzle blast overpressure and gas bubble characteristics of an amphibious rifle when shooting underwater is performed in order to better understand the weapon's capabilities. This inquiry is focused on the 5.56 mm amphibious rifle with 5.56x45 mm underwater ammunition. The results of the experiments indicated that the Rayleigh-Plesset equation may be used to describe and predict the size of gas bubbles. The experimental data may be utilized to compute the law of change of overpressure based on the experimental results. Also, it is a very important base for studying, designing, making, and mastering weapon technology, which are all very important steps in the development of weapon technology

The article presents a method to determine the life of a testing gun that fires 7.62x25mm ammunition. The scientific basis for determining the life of the test barrel is based on the wear of the rifling lands corresponding to the number of shots. The wear of the barrel is determined by the thermal and mechanical effects of the bullet’s driving band on the lands and the grooves. The results show that: With the number of fires being 1000, 2000, 3000, 4000, 5000, and 6000 respectively, the barrel wear is 0.334mm, 0.668mm, 1.002mm, 1.337mm, 1.671mm, 2.005mm, and the muzzle velocity is reduced respectively by 1.15%, 2.06%, 2.98%, 3.67%, 4.36%, 5.28%. The accuracy of the 7.62x25mm ammunition test results is reduced due to this change. In addition, to ensure the accuracy of the measurements, the barrel needs to be replaced when the number of shots is more than 5000 shots. The paper is an important theoretical basis for determining the gun life used to test infantry ammunition.

The article is focused on the application of the reliability and experimental statistics theory to predict the distribution of the cylinder inner diameter and the piston outer diameter post-manufacture for the gas-operated automatic rifles. Besides, the influence of these dimensions on the operation of the automatic system was also studied in 5 cases with the maximum, minimum, and the most probable. The study object in the article is 7.62mm AKM-1 rifles. Research results show that the cylinder inner diameter and the piston outer diameter post-manufacture of  7.62mm AKM-1 rifles follow the normal distribution. The research results of the article can be used to establishing technical conditions for new gun acceptance post-manufacture.