In this paper, the penetration into semi-infinite concrete targets by rigid truncated projectiles is examined. The semi-analytical cavity expansion based penetration formula in Forrestal et al. (Int. J. Impact Eng. 15(4) (1994) 395) and Frew et al. (Int. J. Impact Eng. 21(6) (1998) 489) for ogive-nosed projectiles has earlier been seen to give good agreement with experiments. In Lixin et al. (Int. J. Impact Eng. 24 (2000) 947), this model was extended to truncated-nosed projectiles by introducing two additional empirical constants. In the present paper, Forrestal's approach is expanded to include a larger class of projectile nose geometries, especially flat and truncated noses. The new theory presented here introduces no new empirical constants, and is seen to agree very well with the available experimental data. (C) 2003 Elsevier Ltd. All rights reserved.