The main armament of the TR-85M1 is the 100 mm A308 rifled tank gun (an adaptation of the M1977 towed anti-tank gun made by Arsenal Reşiţa) that was also fitted to the TR-77 tanks. The TR-85M1 has a rate of fire of about 4-7 rounds per minute and can carry up to 41 projectiles inside the tank. The gun barrel is fitted with a bore evacuator and has a thermal sleeve. The TR-85 tanks use a manual loader. The modernized version has a number of improvements to increase the reliability of the gun. The hydraulic buffer was improved by replacing the rubber sealing and the electroerosion of the chrome layer from the hydraulic buffer and recuperator has been removed by changing the design and manufacturing process.