KE Arms makes a unique monolithic polymer lower for the AR15 platform. They’re one piece units that include the core receiver, the pistol grip and the fixed A1 length buttstock. The monolithic design provides the strength that typical polymer receivers don’t have and alleviates the common issue of cracking where the receiver extension (the buffer tube) screws in.
Another way around that is to get rid of the buffer tube altogether. That’s what KE Arms did with their new lowers. They designed them for bufferless uppers like Brownells BRN-180 or the Foxtrot Mike FM15. Rather than a fixed buttstock, these lowers have a rear Picatinny rail allowing you to add the stock of your choice.
The KP-15 Side Folder Lower
I already own three regular KP-15 lowers that I‘ve built into 5.56mm, 7.62x39mm, and 6.5 Grendel carbines. When KE Arms announced the side folding variant this Spring I knew I’d want to try it too so I jumped on the pre order. The lower was delivered in June so I had the rest of my build already planned out by the time it arrived. Let’s take a look at the lower itself first though.
The KP-15 Side Folder is built exactly the same way as the regular KP-15 lowers. In fact it is a regular KP-15 lower that KE Arms removes the buttstock from in a post machining process. They then install an aluminum Picatinny block with a QD socket. The resulting lower weighs just 0.95 pounds. It’s a great start to a lightweight build.
The KP-15 features a big flared mag well that makes reloading easy. You could be drunk or blind, probably both, and still find the magwell on a HP-15. Not that you should probably be shooting if you were either, but you get the idea.
As noted, the grip is integral to the lower. I know some folks may not love that idea, but it adds strength to the design and eliminates the need for a grip screw and washer. Although you can’t add your favorite grip to a KP-15 I do find the stock one comfortable. There are no finger grooves or protrusions and it has textured side panels and a grooved backstrap. If you really wanted to you could doctor it up with some grip tape, or a rubber grip sleeve like a Hogue HandALL. I just left mine stock though, and they work fine.
The Side Folder comes with a Mil-Spec trigger. You have the choice of a mil spec mag release or can upgrade to an ambi mag release for an additional $54.95. The selector switch is also Mil-Spec with the option of upgrading to one of three ambi selectors for an additional $39.95. I stuck with standard Mil-Spec models for both. I don’t know if I’m weird or what, but like a stock GI safety and rarely change them out.
When you pick your lower you have to pick what kind of upper you intend on running. The KP-15 Side Folders will work with either the Brownells BRN-180 or Matador Arms upper, or the FM Products upper. You can run the Brownells or Matador on the same lower, but the FM requires a different lower. I planned on getting an FM Products upper so that’s the option I chose. The KP-15 lower cost with standard Mil-Spec parts is $324.95. That includes the lower, all of the fire control parts, the mag release, bolt hold open, and the take down pins. The take down pins on a KP-15 lower are different from your standard AR take down pins and are not captive. You can remove them entirely from the lower during disassembly. Just don’t lose them.
If you’re a PCC guy, KE Arms also makes the KP-9 Side Folder. Specs are similar to the rifle lower and they’re made to work with the Brownells BRN-9 or Matador Arms uppers. Price is still $324.95 for a Mil-Spec model. As of this writing they’re showing 4 to 6 weeks out for delivery, but you can pre-order.
The Mike-15 Gen 2 Upper
Since the KP-15 lower is so light weight I had decided that I wanted an overall light, compact build. It would compliment the fact that I could put a side folding stock on this project. I went with a Foxtrot Mike Mike-15 Gen 2 complete upper with a 12.5 inch barrel and a forward positioned, side charging handle.
Foxtrot Mike generally uses the .223 Wylde chamber for their uppers, which will work with either .223 Remington or 5.56mm NATO equally well. Not long after I got my upper I saw that they started offering the same set up in .300 Blackout as well. Had that been available when I grabbed my upper I’d have probably gone with the .300 for this build, but the .223 Wylde was fine.
The Mike-15 upper uses a proprietary direct impingement system with a mid length gas that allows the rifle to operate without the need for a buffer tube. It will work with any standard Mil-Spec lower. Foxtrot Mike even includes a Picatinny rail adapter with the upper so can convert your basic lower into a side folder. You do need to use this adapter with the Gen 2 uppers as it has an integrated recoil buffer designed to work with the upper. That’s the reason KE Arms offers a specific KP-15 lower for the Mike-15 uppers as well.
My 12.5 inch barrel has a 1:8 twist and is made from 41V50 match grade barrel that’s vacuum, stressed. It has a Melonite finish and a burnished chamber. The muzzle uses a common 1/2×28 thread and is fitted with a 4 port Micro Brake. Due to the bufferless design, the Mike-15 uses a proprietary bolt of 4342 vacuum treated steel with a Melonite finish. FM uses an 11.75 inch M-LOK handguard finished in a black Type III hard anodizing on the 12.5 inch barrel upper.
The Gen 2 upper uses a forward mounted charging handle. From the factory it’s positioned on the left side, much like an HK MP5 or G3. It’s a 4 position unit though and can be switched to the right side as well and you can position the actual handle in the up or down angled position. Left side up works for me so I left it as it is. The charging handle is non reciprocating so there are no concerns with it interfering with your preferred forend grip.
MSRP on the Mike-15 upper is $529.00, and that includes the Picatinny Rail adapter.
Magpul Stock and Accessories
To take full advantage of the side folding stock, I decided to SBR this build. I could have braced it, but I wanted an actual stock. For the rest of the build I used Magul accessories since they were a one stop shop for what I needed. I added a M-LOK Paraclip Sling Mount, along with a simple MS1 Lite sling. For the stock I used the newly released UCS side folder. Since this was a pretty modern build, especially compared to my usual retro clones, I picked up a trio of 20 round TMAGS and a trio of 30 round TMAGs.
The UCS stock fits any standard M1913 Picatinny rail. So it will go on just about any large format pistol or rifle, or shotgun adapter out there. It folds to the left side of the receiver and is adjustable for length of pull. Lock up is solid and it’s comfortable to use. There’s a detachable cheek rest that snaps on. There’s a reversible QD swivel socket for sling attachment.
With the stock folded my FM/KP-15 is just under 23.5 inches in overall length. With the stock open and fully extended its 33.25 inches. You knock off 3 inches with the stock collapsed. Weight is 6.14 pounds with sling, optic and empty magazine. It isn’t the smallest SBR I’ve built, but it’s a good balance of compactness and practical size.
Gideon Optics
I’ve been working with a variety of Gideon Optics over the summer, and for this build I had an Advocate Micro Prism sight, which worked out perfectly. Travis Pike just did a full review of this optic here on TTAG as well. It’s a non magnified 1×20 sight with an etched reticle. The sight is made from 6061-T6 aircraft aluminum with a black anodized finish.The sight is shockproof to 1000G’s of force and waterproof for up to 30 minutes to one meter of submersion, as well as being fog proof. It mounts to any M1913 Picatinny rail and positions the pupil centerline 1.6 inches above the rail. It works well on AR’s but there’s an optional low mount available too if that works better for your set up.
It’s powered by a single CR2032 Lithium battery and has either a green or red reticle. I went with a green model since I find that it stands out better against most backgrounds. The 2032 battery provides an impressive 30,000 hours of life. Coupled with the motion activated system that powers down after 4 minutes without movement, but wakes up immediately when movedm and you aren’t going to be changing batteries often. Still, I like the idea that even if you did run the battery dry the etched reticle still keeps you in the game.
The optics quality on the Gideon is excellent with a crisp sight picture and good light gathering characteristics. The Advocate is parallax free to 100 yards and gives you a 79 foot field of view at that range. The reticle itself is a triangle within a circle that I found easy to pick up and fairly precise. For fast shots close in, just drop the circle or triangle on target. For more precise shots further out use the triangle itself or the tip of the triangle as your aiming point.
Sight in was easy too, and I didn’t need to do much adjustment. I’m not sure if it’s how they’re set up from the factory, or If I’ve just been lucky so far. I’ve used four Gideon sights over the past few months and none of them needed much adjustment. They seemed pretty well centered right out of the box.
MSRP on the Gideon Advocate is listed at $299.99, but they’ve been showing on sale for $249.99. They come with Gideon’s lifetime warranty too which covers just about anything short of outright, deliberate abuse.
Range Time
I’ve had my FM/KP-15 out three times now and am creeping up on 500 rounds through it so far. Not a long term torture test by any means, but so far so good. If there’s an ammo company that would like to sponsor me I’ll gladly put 10,000 or so through it.
Since I got a Mil-Spec fire control kit in my lower, the controls are typical AR. Nothing fancy there, which is how I like it. The forward charging handle on the upper is slick. It’s a nice feature if you’re moving from a platform that already uses a similar set up and you are used to it. Even if you’re a dedicated AR person, you adapt to it easily.
It works in conjunction with the regular AR bolt hold open on the lower fine too. I do wish you could lock the bolt back with just the charging handle. I found trying to lock the bolt open without a mag inserted a little awkward without an ambidextrous bolt hold pen. FM lowers do have that, so it is probably less of an issue if you have an all FM set up. But if you’re putting a Mike-15 on your existing lower or the KE Arms one it takes some finagling since the charging handle and standard bolt hold open are both on the same side of the gun.
For testing I’ve used a mix of 55gr, 62gr, and 77gr loads from a variety of manufacturers both commercial and military surplus. I used the Magpul TMAGs for all of my shooting. They worked well with my Podavach loader. Reliability has been 100%. The mags load easily into the big flared mag well and lock in without issue. They drop free smoothly during reloads as well. Being able to visibly check the loaded status on the TMAGs, and general round count, is handy as well.
The FM upper and Gideon optic make a good pair and shooting tight groups out to 50 yards was easy with best groups sitting right around an inch, and nothing bigger than 2 inches accounting for called fliers. Past 50 yards the non magnified optic and my mid 50’s eyes start to allow things to open up a bit, but the mechanical accuracy of the upper is there. With that said, I can hit the steel gong on my club’s 300 yard range more than not with this set up. From a bench with a sandbag rest that is. I’m not sure exactly of the size but it’s probably a 15 inch or so gong. Not bad for a 12.5 inch barrel .223 Wylde.
A Thoroughly Modern Package
The combination of the KP-15 Side Folding lower and the Mike-15 Gen 2 upper make for a sleek set up. Particularly with the 12.5 inch barrel and Magpul UCS sidefolder, this makes for a great truck gun. The short overall length would make it handy getting in and out of a vehicle, and for clearing inside buildings as well. I’m happy with the Gideon Advocate prism sight on it too. It does add much bulk or weight to the build and I find the reticle very easy to use. The fact that it isn’t solely dependent on batteries lets me skip adding back up irons too. I don’t expect anyone to run out and do a clone of my build exactly, but I can say that if you’re thinking about your own build all of the things I put into mine worked great together.
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