The M42 was used as a close and close-mid range weapon issued to individual troops. Especially used by special forces, Marines and CQB troops, it was most effective at shorter ranges, and had stopping power capable of taking down even the heaviest infantry units at its optimum ranges. Its ammunition types were diverse and varied, providing a tailored response to each situation. It was complimentary to the M105 Shotgun, being more accurate, larger and capable of higher rates of fire, while utilising a smaller ammunition and being less portable.
The M42 Shotgun used the 12 Gauge shotgun shell, of 2.75 inch length. This cartridge was less powerful than the 8 Gauge shell used in the M105 Shotgun, with less stopping power and shot spread. The advantages included reduced size and recoil, which increased the weapon's controlability characteristics in burst or automatic fire modes; its faster rate of fire compensated for decreased damage per hit. There were various forms of ammunition in the 12 Gauge calibre, with the M1071 Shot and M1074 Incendiary Flechette being most widely used.
M1071 Shot: Alongside the M1074 Incendiary Flechette, the M1071 Shot Shell was the standard shell issued in the 12 Gauge calibre. The shell itself contained either 50 smaller or 20 larger spheres of CVT (Chromium Vanadium Tungsten) and Austenitic Steel alloy. Though actual spread varied according to the weapon itself, the shell generally possessed good range qualities. This was coupled with high stopping power, shield depleting and armour piercing characteristics, which meant that a single discharge could usually overcome all but the strongest adversary within its optimum range.
M1072 Sabot: The M1072 Sabot shell was a specially shaped, two-stage cartridge. It had an outer jacket that enabled it to travel further, outside a standard shot of 40 small spheres of molecularly compressed CVT/Steel alloy, or alternately 15 larger ones. The shell had a long range but relatively low penetration.
M1073 Flechette: M1073 Flechettes were similar to the M1072 Sabot, though replaced the shot with hundreds of CVT/Steel alloy subprojectile barbs or flechettes. These had high range and were usually deadly to armoured targets. The M1073 was in most respects superceded by the M1074.
M1074 Incendiary Flechette: The M1074 contained roughly 60 small, fin-stabilised armour piercing flechettes. These flechettes were composed of the 'TC3' alloy (made up of tungsten, cerium and copper carbide), and had indenciary, self-sharpening and pyrophoric properties similar to uranium without associated radiological effects. The flechettes had powerful armour-piercing ability and secondary incendiary effects to do high damage after initial contact with a target.
M1075 Explosive Shot: The M1075 Explosive Shot Shell was a standard shell filled with approximately 30 small explosive projectiles, utilising a powerful plasma-based explosive. Penetration was low, but actual power was high, especially against shielded targets; this resulted in their use being mainly tailored towards shielded enemies.
M1076 Slug: The M1076 Slug was essentially a crude rifle round, using a rifled, hollow slug consisting of a lightweight deforming ballistic cap and a CVT/Alloy exterior. Subtypes of this round include the M1076A Explosive Slug, which saw the hollow interior filled with a plasma-based explosive, the M1076B Armour Piercing Slug, which contained a TC3 alloy penetrator, and the M1076C Incendiary Slug, the interior of which was filled with an incendiary material.