The following tables show armor penetration characteristics for U.S. 37mm, 75mm, 76mm, and 90mm guns against homogeneous and face-hardened armor. The tables are taken from the July 1944 field manual FM 17-12 Tank Gunnery.
From top to bottom, the ammunition types shown are (i) 90mm, A.P.C., M82, 2650 f/s; (ii) 3″ (76mm) A.P.C., M62, 2600 f/s; (iii) 75mm, M3, A.P.C., M61, 2030 f/s; and (iv) 37mm, A.P.C., M51B1 & M51B2, 2900 f/s.
FM 17-12 Tank Gunnery gives a brief useful summary of ammunition types for gunners:
(1) Armor piercing (AP). This ammunition is a solid projectile with a tracer element. 37-mm shot, AP M74, 75-mm shot, AP M72, and 76-mm shot, AP M79, are in this class. This is used for training.
(2) Armor piercing capped (APC). This ammunition is a solid projectile with an armor piercing cap, a windshield, and a tracer element. The windshield streamlines the projectile, thereby reducing wind resistance. The armor piercing cap is of alloy steel, hardened to insure a very hard face with a tough and relatively soft core in contact with the projectile. The cap serves as a guide or cushion for the projectile. In this class are 37-mm shot, APC M62, 75-mm projectile, APC M61, and 76-mm projectile, APC M62. The 75-mm and 76-mm projectiles have a small cavity for high explosive filler. This ammunition is painted black.
(3) Armor piercing, capped with high explosive filler. This ammunition is the same as armor piercing capped ammunition except that it contains an explosive filler and a base detonating fuze. This is the most effective high velocity armor piercing ammunition because the projectile bursts after penetration. 75-mm projectile, APC M61, with BD (base detonating) fuze, M66A1, and 76-mm projectile, APC M62, with BD fuze M66A1 are of this type. Armor piercing projectiles containing high explosive filler are painted olive drab color with yellow lettering.
(4) High explosive-antitank (HEAT). 150-mm shell, HEAT, M67, is a low velocity armor piercing shell of the hollow charge type. It employs the BD fuze, M62. This ammunition is painted olive drab with yellow letters. Inert HEAT shell is painted black and is used for training purposes. The M67 will penetrate 5.5 inches of armor at all angles between 0° and 60° and at all ranges the gun will fire.