This seems to be a current hot debate:
Magpul M-LOK – Modular Locking accessory mounting system
Bravo Company KMR – KeyMod Rail system
The science is fairly straightforward…M-LOK has more surface area, thicker edges (no 100 degree cone cut) so more material behind the slots, flat on flat engagement, and all the things discussed in the M-LOK FAQ on the Magpul website. KeyMod was an evolutionary step into negative space attachments, or at least a slight change of AI KeySlot, but just wasn’t designed by an engineer or with engineering behind it with all of the material considerations in play.
Some folks are happy with KeyMod mounting lightweight accessories without much abuse, and that’s cool. Heavier stuff, high round counts, and generally treating the rifle like a tool ends up being really, really hard on KeyMod, and things can get loose, seats creep and crush, etc. The pullout, drop, high round count firing, shaker table, leveraged pullout, etc testing of initially KeyMod, and then KeyMod vs M-LOK was what led down the path to release M-LOK in the first place.
Colt CA and other MFG have done their own evaluations, and that’s why you saw a lot more M-LOK at SHOT this year. A bunch of other entities have adopted or ordered M-LOK as the solution of choice, and some additional third party testing is currently underway, so when all that comes out, you won’t have to take anyone’s word for it. That’s the way I see it. There is a thread in the P&S Pro Facebook group that has it straight from the horse’s mouth on some of the shortcomings I’m talking about that started the professional user pendulum swinging away from KM.
The easiest way to describe this battle:
VHS versus Betamax and the porn industry is choosing M-LOK.
The link to that group mentioned above :