The 3" GMC M10 tank destroyer was based on the medium tank M4A2, and had the same main gun as the heavy tank M6. M10s were built with single-piece final drive and differential covers, and the turret only had a partial roof over its front third. This allowed better visibility and easier servicing of the weapon, at an obvious cost of increased vulnerability. The hull and turret on the M10 both took advantage of armor sloping, and both were fitted with bosses to which additional armor could be attached should the need have arisen. The turret of the M10 was five-sided, including the gun shield in front. Two triangular counterweights totaling 3600lb (1600kg) were added to the rear of the turret to balance the heavy 3" gun in the front. These greatly eased turret traverse. On late production M10s, the applique armor bosses were deleted from the turret and hull sides, but remained on the hull glacis, and the turret counterweights were changed to a "duckbill" cross-section. The shape of the turret rear was altered in late-production vehicles to improve working space.

The M10A1 was based on the medium tank M4A3, and was similar to the M10 except for the Ford GAA engine; mounting the GAA gave the M10A1 larger air intake grilles on the top of the hull rear.