The ships were armed with a main battery of twelve 14-inch (356 mm)/50 caliber Mark IV guns in four, three-gun turrets on the centerline, placed in two superfiring pairs forward and aft of the superstructure.
Unlike earlier American battleships with triple turrets, these mounts were true three-gun turrets, in that each barrel could elevate independently.
They fired a 1,400 lb (640 kg) shell with a 470 lb (210 kg) bursting charge.
The guns had a muzzle velocity of 2,800 ft/s (850 m/s).
Early in their careers, the New Mexicos and the Tennessee class experienced excessive dispersion of shot.
After extensive testing, it was eventually discovered to have been caused by overly lengthy chambers, which allowed a gap between the shell and the propellant charges.
The problem was eventually corrected with the Mark VII gun.
The guns were supplied with 100 shells each and they were capable of a rate of fire of about one salvo per minute, as demonstrated by extensive testing with Idaho in October 1942.

The secondary battery consisted of fourteen 5-inch (127 mm)/51 caliber guns mounted in individual casemates clustered in the superstructure amidships.
Initially, the ship was to have been fitted with twenty-two of the guns, but experiences in the North Sea during World War I demonstrated that the additional guns, which would have been placed in the hull, would have been unusable in anything but calm seas.
As a result, the casemates were plated over to prevent flooding, leaving only the fourteen guns in the superstructure.
Of these, ten were located on the forecastle deck and the other four were in open mounts on the shelter deck.
Each gun position contained twenty-four rounds of ready-use ammunition, with further munitions stored in the magazines below.
The guns were the Mark VIII type, which had a muzzle velocity of 3,150 ft/s (960 m/s) firing a 50 lb (23 kg) shell.

The secondary battery was augmented with four 3-inch (76 mm)/50 caliber guns in high-angle mounts for anti-aircraft defense.
The guns fired a 13 lb (5.9 kg) shell at a velocity of 2,700 ft/s (820 m/s).

In addition to their gun armament, the New Mexico-class ships were also fitted with two 21-inch (530 mm) torpedo tubes, mounted submerged in the hull, one on each broadside.
Both tubes were located in a single torpedo room forward in the hull.
Each tube was supplied with a total of six torpedoes, which were Bliss-Leavitt weapons of the Mark VII type; these carried a 321 lb (146 kg) warhead and had a range of 12,500 yd (11,400 m) at a speed of 27 kn (50 km/h; 31 mph).
The ships were armed with a main battery of twelve 14-inch (356 mm)/50 caliber Mark IV guns in four, three-gun turrets on the centerline, placed in two superfiring pairs forward and aft of the superstructure. Unlike earlier American battleships with triple turrets, these mounts were true three-gun turrets, in that each barrel could elevate independently. They fired a 1,400 lb (640 kg) shell with a 470 lb (210 kg) bursting charge. The guns had a muzzle velocity of 2,800 ft/s (850 m/s). Early in their careers, the New Mexicos and the Tennessee class experienced excessive dispersion of shot. After extensive testing, it was eventually discovered to have been caused by overly lengthy chambers, which allowed a gap between the shell and the propellant charges. The problem was eventually corrected with the Mark VII gun. The guns were supplied with 100 shells each and they were capable of a rate of fire of about one salvo per minute, as demonstrated by extensive testing with Idaho in October 1942.
The secondary battery consisted of fourteen 5-inch (127 mm)/51 caliber guns mounted in individual casemates clustered in the superstructure amidships. Initially, the ship was to have been fitted with twenty-two of the guns, but experiences in the North Sea during World War I demonstrated that the additional guns, which would have been placed in the hull, would have been unusable in anything but calm seas. As a result, the casemates were plated over to prevent flooding, leaving only the fourteen guns in the superstructure. Of these, ten were located on the forecastle deck and the other four were in open mounts on the shelter deck. Each gun position contained twenty-four rounds of ready-use ammunition, with further munitions stored in the magazines below. The guns were the Mark VIII type, which had a muzzle velocity of 3,150 ft/s (960 m/s) firing a 50 lb (23 kg) shell.
The secondary battery was augmented with four 3-inch (76 mm)/50 caliber guns in high-angle mounts for anti-aircraft defense. The guns fired a 13 lb (5.9 kg) shell at a velocity of 2,700 ft/s (820 m/s).
In addition to their gun armament, the New Mexico-class ships were also fitted with two 21-inch (530 mm) torpedo tubes, mounted submerged in the hull, one on each broadside. Both tubes were located in a single torpedo room forward in the hull. Each tube was supplied with a total of six torpedoes, which were Bliss-Leavitt weapons of the Mark VII type; these carried a 321 lb (146 kg) warhead and had a range of 12,500 yd (11,400 m) at a speed of 27 kn (50 km/h; 31 mph).
New Mexico-class battleship