Neo035 shows the process and performance of upgrading an S&T Mosin-Nagant airsoft rifle with a complete internal kit from TNT Studio to improve its range and accuracy. He compares the stock rifle to the modified one, which features a smoother bolt action, a significant increase in power (about 100 FPS gain with an M130 spring), and an extended effective range from approximately 58 meters to 65 meters, noting that the upgrade makes it much easier to consistently hit targets at long distances. He warns that upgrading the spring without changing other internal components could damage the rifle and result in an overly stiff operation.