AM-M58 500 Lb. SAP (Semi Armor Piercing) Bomb

Semi-armor-piercing bombs have bodies similar in contour to those of armor-piercing bombs. SAP bomb bodies are of thinner wall construction than those of the armor-piercing series. With but one exception (2000-lb Ml03) these bombs will accommodate both nose and tail fuzes. Most tactical uses do not require a nose fuze; in which case, the nose fuze seat cavity is fitted with a solid steel plug. The semi-armor- piercing series was developed to provide greater penetrative ability than that afforded by comparable weight general purpose bombs.
When used in dive bombing, trunnions were installed.

(ORDNANCE PAMPHLET 1280 (FIRST REVISION)
AIRCRAFT BOMBS)

Armored ships, reinforced concrete construction, pill boxes, and bunkers are vulnerable targets for this type of bomb.
On June 6, Norman Jack "Dusty" Kleiss accompanied Enterprise's dive bombers in a mission that helped sink the Japanese cruiser Mikuma. Kleiss's bombs struck near Mikuma’s smokestack.[7] Kleiss was the only pilot to score three direct hits with a dive bomber plane during the Battle of Midway. For his participation in the battle, Kleiss received the Navy Cross in November 1942.