So you’re building an AR-style rifle. You need to make your choice about handguards, right? It’s no longer the 60’s or 70’s when everything out there that looked like an M16 or MP5 had a tropical style handguard that was (mostly) useless.
No way, not anymore. Today complete AR15 uppers are available with a wide range of rail systems ranging from quad rails to M-LOK rail systems that are impressively modular, versatile, and expandable.
Moreover, the Picatinny rail isn’t the only kid on the block. Nowadays you have choices. So let’s cover the virtues of M-LOK rail systems compared to traditional quad rail uppers.
Quad Rail Uppers
If there’s one modern rail system on the market that has some serious staying power, it’s the Picatinny rail system that has been around for more than 30 years now.
Consisting of a section of rail with slots and grooves, the Pic rail is recognizable to basically anyone that’s ever fired an AR. They’re now universal elsewhere, too, and there is a whole industry devoted to making accessories for Pic rails.
But how does this factor into the name “quad rail,” you may ask? Because the two are not exclusive. As the name might suggest, a quad rail is simply a handguard with four Picatinny rails distributed around it. One on the top, one on the bottom, and one on each side of the handguard.
With a quad rail upper, you get way more bang for your rail system than you would if you just had a length of Picatinny rail over the receiver. Four times the bang for your buck, to be exact.
As with any conventional Pic rail configuration, the main benefit is versatility. There are thousands of shooting accessories out there that are Pic-rail compatible, ranging from scopes and optics to sling mounts, brass catchers, backup iron sights, and pretty much anything else you can imagine.
But with a quad rail, the fun doesn’t stop with that one Pic rail over the receiver. You have rails on the sides and under the platform that are also ripe for the proverbial accessorization. With a quad rail, you can mount a scope over the top, plus a light, laser, brass catcher or backup AR15 sights on the sides, with enough room yet on the bottom to mount a folding vert grip or anything else your heart desires.
Also, a quad rail offers other benefits besides this flexibility. With a quad rail upper, you get a very high degree of flexibility. You can mount accessories as far forward as back as the railed upper will allow.
On top of that, you get the legendary durability of the Picatinny rail system. Lovingly (and perhaps less-than-lovingly) referred to as a “cheese grater” the quad rail is tough as nails. Too tough for some; handling some without gloves is a trip. Some manufacturers even make special rail covers for the sections you don’t use to make the handguard more of a grip and less of a hand-grater.
There’s a tradeoff here, though. Because of the bulky, durable nature of the classic Pic rail, they are very heavy. Now take that, and magnify it by a factor of four. To put it lightly (no pun intended) quad rail uppers are heavy. And the worst part is, if you add rail covers to make them more comfortable, you’re just adding weight.
There are things you can do to make them lighter - like choosing a shorter quad rail upper, but at a point, there are diminishing returns.
Which brings up a viable modern alternative: M-LOK rail systems.
M-LOK Rail Systems
In contrast to Picatinny quad rail uppers, M-LOK rail systems are much newer. These were designed by Magpul starting in 2007 and named the MOE Slot Systems.
In contrast to Pic rail systems, M-LOK rail systems consist of a much lighter, thinner metal skeleton punctuated by oblong metal slots. To mount an accessory on an M-LOK system, you insert the device into the slot and tighten the bolt that secures it - quite different from a Pic rail accessory.
There are numerous benefits to the use of M-LOK systems. One is that they are much lighter. It is far easier to carry a rifle with a long barrel (and therefore long handguard) that’s equipped with M-LOK technology than it is to carry a 20” quad rail upper.
On top of weight, the M-LOK is (cough) just more ergonomic and user friendly. If “cheese grater” didn’t tell you all you needed to know, please go back and read the last section more closely. It can be very uncomfortable to shoot a rifle gripping the naked quad rail upper - not so with the smooth, sleek lines of the M-LOK system.
On top of that, you don’t need to add rail covers (and therefore, weight) to an M-LOK rail system to make it ergonomic enough to shoot with if you have uncovered rail sections.
There’s another draw. Magpul designed the M-LOK system to be open-source - which means anyone can use the technology. That has kept barriers to entry low, and even though there aren’t as many M-LOK accessories out there as Pic rail accessories, more are getting added by the year.
Also, modern M-LOK rail systems are available in both metal (usually lightweight aluminum) and polymer, so you can take your pick there.
One more thing: there are recoil-mitigation lugs you can get for M-LOK systems, making the mounts recoil-resistant. That can be a problem with some Pic rail accessories.
Start with Either AR15 Upper Here at MCS Gearup
Getting ready to start a new build with either a quad rail upper or an M-LOK rail system? The best one for you ultimately will come down to preferences.
If you like the durability and don’t mind the weight, go with a quad rail upper. If you need a lower-weight alternative, M-LOK is definitely a better choice. Either way, if you’re looking for a complete AR15 upper, we have options for both.
Other than that, they are both excellent rail systems, and we carry railed uppers in both configurations, as well as a wide range of Pic rail and M-LOK accessories.