Although designed with no consideration for the anti-tank role, the SU-152 proved to have surprisingly good anti-tank capabilities due to the ML-20S's extremely heavy HE projectiles. Standard doctrine for purpose-built AT guns of the period universally relied on small, dense solid projectiles propelled to high velocities, optimized for punching through armor. Since the SU-152, like all SU-series self-propelled guns was not designed with tank killing in mind, no AP projectiles were issued to crews and no initial tests against armor were conducted. However, tests performed on captured Tiger tanks in early 1943 showed that the SU-152 was able to destroy them at any range with a fair degree of reliability (the only vehicle then in Russian service capable of doing so) by simply blowing the turret off the vehicle through sheer blast effect. This fortuitous discovery spurred massive SU-152 production and the formation of self-propelled artillery units, which then functioned as ersatz heavy tank destroyer battalions.