Naval Surface Warfare center, commissioned by United States Special Operations Command (USSOCOM), conducted an evaluation of modular handguards. These popular accessories were tested for toughness and reliability. Test was part of 2 current programs. Suppressed Upper Reciever Group which focuses on modernizing M4A1 Carabine and Advanced Sniper Rifle, which center on finding a replacement for repeating rifles used by marksmen.
Off the shelf solutions were ordered in both KeyMod and M-LOK standards. Aero Precision, Midwest Industries and Seekins delivered 3 sets each, which were installed on identical M4A1 Carabines. Over duration of the test handguards were subjected to rough treatment, drops, and also static tested. Durability and repeatability were judged.
Both variants stood their ground on rough handling and durability tests. However, repeatability trials uncovered a major difference between M-LOK and KeyMod systems. Rail-mounted measuring device showed rather large POA shift difference between variants. 0.0 to 6.6 MOA for M-LOK and 0.2 to 14,6 MOA for KeyMod. Static load tests showed also, that M-LOK is 215 percent more durable than KeyMod. However, the latter allows for lot easier attachment of accessories while aligning it.
These trials probably determined, that US Armed Forces will choose M-LOK variant, as it provides better stability of weapon-mounted equipment.