Abstract: A novel facility for tensile testing at the critical impact velocity was designed in a gas gun system. This facility consists of two assemblies, firstly, a gas gun system to propel the projectile and secondly, the tension mechanism to grip and strain the specimen bars. The critical impact velocity experiments in tension of oxygen-free high-conductivity copper were carried out using the novel facility. A numerical simulation was presented for uniaxial tensile testing at the critical impact velocity in complete thermal coupling. In case of necking, the plastic constraint factor, the void growth and coalescence were considered. The computed results with the Johnson-Cook or Zerilli-Armstrong constitutive relations, respectively, show that the Zerilli-Armstrong constitutive relation give a better prediction of the experimental critical impact velocity in tension for oxygen-free high-conductivity copper.