The M-1918 Mil-Std rail had enjoyed a monopoly on firearms mounting solutions until the KeyMod and MLOK accessory interface systems came around in the early 2010s. Both of these systems had the idea of using the concept of “negative space” (i.e., holes) instead of the rails used by the Picatinny and Weaver.
Some people like Picatinny handguards for their modularity and versatility, but others despise them for their rough texture, which becomes especially noticeable when they scrape against a shooter’s offhand when firing a rifle with high recoil. Rifles with smooth handguards and KeyMod/MLOK systems are both more comfortable and lighter thanks to the fact metal is removed from the handguard to create the mounting systems.
Rail pieces like the Firefield Edge or Verge enable shooters to take advantage of the light weight and smooth surfaces of the KeyMod and MLOK without the need to buy a brand new MLOK or KeyMod-exclusive accessory.
But which one of these two mounting systems is better? US Special Operations Command asked the same question and pitted the two mounting solutions against each other in a contest that would determine their strength and stability, testing their tolerances to the limits.
During its study, USSOCOM subjected the MLOK and KeyMod handguards to an array of torture tests to measure their mounting consistency, endurance under sustained fire, endurance under rough handling conditions, ability to withstand being dropped from a height, and retention strength.
To determine how well the mounting systems would hold consistent zero, KeyMod and MLOK handguards outfitted with lasers were placed in vises and pointed at a grid target. The lasers were then removed and reinstalled on the handguards, after which their point of aim shift was recorded.
KeyMod consistently performed worse than MLOK, with point of aim drifting by as much as 14.6 MOA off target. For comparison, the worst results from MLOK showed a drift of only 6.6 MOA at worst and no drift at all at its best.
To measure their endurance, handguards outfitted with a weapon light, laser sight, and flash hider shim set were run through a recoil machine which simulated 10,200 rounds of automatic fire, a total of 340 magazine changes.
Of course, testing the number of rounds a component can handle before breaking has more to do with recoil than actual endurance. For true rough handling, weapons with MLOK and KeyMod handguards were tossed from a height of five feet onto a solid steel plate.
The KeyMod handguard consistently proved to be worse than its MLOK counterpart. In the worst cases, the attached flashlight flew as far as eight feet from the weapon it was attached to, or the handguard came off completely. Meanwhile, the more resilient MLOK handguards proved their superior ruggedness by showing slight deformations at the very worst.
USSOCOM’s comprehensive testing proved the MLOK was consistently more durable and reliable than its KeyMod counterpart. This, however, does not mean that the KeyMod system is always a bad choice. After all, many opt for a KeyMod or MLOK adaptor for a Picatinny rail, since most accessories still make use of the modular Picatinny system.
Still, the non-Picatinny accessory systems have their advantages. One loses nothing but weight when installing an MLOK or KeyMod handguard for an FN FAL, PTR, G36, or an AK. Finding compatible accessories shouldn’t be a problem either, as long as shooters utilize adaptors like the Firefield Edge or Verge.