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KeyMod 101: Review and Installation

The KeyMod rail is one of the newer whizz-bang rail systems out there for AR 15s. Our writer’s time in the Marines was spent with rifles equipped with quad rails, so we were a bit skeptical when KeyMod (and M-Lok) came out – we quickly realized how innovative they are. KeyMod handguards are modular handguards that aim to replace quad rails on modern rifles. They feature ‘keyholes’ that allow the user to attach rails only where they need them. There are also KeyMod accessories that attach directly to the rail without the need for picatinny rails. KeyMod rail systems have become popular enough they are now standard in many AR 15 Kits, including our popular 16” CHF AR Rifle Upper. Even Tier 1 military units have adopted the technology – so why should you? Find out.

KeyMod Advantages

KeyMod handguards are often much lighter in weight than quad rail systems and they allow the same amount of “rail” estate. They aren’t just lighter, they’re thinner, too, and usually more comfortable to grip. Picatinny rails can act like cheese graters on your hand and after a long range session, you’ll start to feel the pain. 

KeyMod is an open-source system. Anyone can build KeyMod rails and accessories for the platform. This tends to make KeyMod rail attachments and accessories both affordable and varied. This “rail renaissance” has given us a multitude of different length rails, direct mount foregrips, bipods, and flashlight mounts that attach to KeyMod rails and integrate effortlessly.

How it Works

Using the KeyMod rail on your AR 15 kit is pretty simple. Attaching rails and accessories directly to the rail system is pretty easy to do, all you need is an appropriate Allen wrench. If you look at KeyMod rails you’ll notice the attachment point acts, well, like a key. The female opening on the rail accepts the male end of the attaching accessory nut. Once inserted, you simple slide the accessory in the direction of the KeyMod’s smaller extension. Then you just tighten your accessory to lock it in!

Installing KeyMod Accessories, Step 1

Looking at any KeyMod accessory, you’ll see the thin nut we’re talking about. This nut will only fit in the larger section of the KeyMod slot. Depending on the size of the accessory or Picatinny rail you could have anywhere from 2 to 6 of these nuts. 

Installing KeyMod Accessories, Step 2

Like we described, just place these nuts into the larger KeyMod slot and then slide the accessory forward. In the forward position, you use the Allen wrench to tighten the nut. 

That’s it! Once it’s tightened down, you’re ready to rock and roll.

Picking a Quality KeyMod-Equipped AR 15 Kit

KeyMod rails are everywhere. Most are good to go out of the box, but some are sketchy – remember, this is an open-source platform after all. We only include the highest quality KeyMod rails with our rifle kits, like our popular stainless kit below. 

AR-15 Build Kit - 5.56 (Keymod Upper & 16" Stainless Steel Barrel) with Fire/Safe Engraved 80% Lower Receiver

Because KeyMod systems are so thin and lightweight, they also work great on AR 15 pistols. Our KeyMod rail systems are designed to last and they’ll withstand serious pressure and abuse t for thousands of rounds. Our KeyMod rails are also all designed to be free floating, which gives you higher mechanical accuracy.

The golden rule with KeyMod rails is the same golden rule for every AR 15 kit we sell. Quality matters. A cheap rail system isn’t going to last for thousands of rounds, and you run the risk of out of spec rails, out of spec key slots, and general crappiness.



DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At AR-15LowerReceivers, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.


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