Stripped KE Arms KP-15 Polymer Lower Receiver


WARNING! DO NOT Dry Fire your KP-15 without the upper in place.

Doing this can damage the receiver wall in front of the hammer.

Note: After first range session, remove buffer assembly from lower receiver by pressing down on buffer detent and pulling out buffer and spring. The cycling of the action may have removed additional plastic flash caused by the manufacturing process that was not removed during our post-weld processing. Shake out any debris or use compressed air to clear out the buffer tube.


• The KP-15 has a lifetime warranty for normal use.

• Sling Attachment points wearing out is not grounds for a free receiver replacement.

• If the receiver breaks through misuse or neglect, we will replace it ONCE for $65.00.

• Structural modifications including but not limited to: unauthorized stock shortening, removal of material, and dyeing the receiver void the warranty.

• If you intend to register your KP-15 as an NFA weapon test it thoroughly before doing so in a Title 1 Configuration. Once you Form 1 or Form 2 it, you are legally the manufacturer and we cannot service or support it as easily. Should your receiver require warranty replacement we can only replace it with a title I receiver and we are not responsible for tax stamps or NFA fees.

• Cerakoting: If you intend to have your KP-15 Cerakoted we recommend you use We Plead the 2nd ( as they are experienced in coating polymer receivers and have our authorization. The bake should be done at low temperatures

(<190 Degrees F) and with an upper in place to prevent warping.

Features Include

• Compatibility with most common AR15 uppers and lower parts kits

• Flared magwell to make reloads under stress easier to perform.

• A1 Length 13” Length of Pull (LOP) Buttstock to fit a wide range of shooters

• MLOK Slots at rear of stock for sling attachment points or run a strap through it for simple sling attachment

• Holes at the front of the stock for QD socket inserts for more sling attachment options

Technical Notes

• The KP-15 receiver uses a Carbine buffer and spring. Do NOT use anything other than standard carbine buffers and round springs or the JP SCSS in the KP-15.

• The front lugs where the upper receiver attaches are intentionally snug. The upper should be pushed down in place from the top between the lugs. The rear take down pin may need to be tapped in and out with a hammer depending on upper fit.

• The Take Down and Pivot Pins have the detents built into them; eliminating the spring and detent holes in the lower increases durability. Pins insert left to right. Spare pins are available from KE Arms.

• The buffer detent is held in place with a 5/64” x 1” Roll Pin

• The KP-15 is compatible with some cassette* style match triggers including the KE Arms DMR and SLT units. The retention system of these triggers with D-Clips in the bushings to retain the fire control pins makes them better suited for use in the KP-15 than other designs that require captured pins.

• The hammer pin area is wider for durability. Standard AR15 hammer pins can still be used but we offer a longer hammer pin for customers preferring a flush pin for aesthetic reasons.

• Safety selector spring and detent load from the top and then the selector is slid over them. Disassembly of the fire control group should only be done by an experienced gunsmith or certified armorer.

• The KP-15 is compatible with standard AR15 uppers in calibers including .223/5.56mm NATO, .300 Blackout, 6.5mm Grendel, 6.8mm SPC; make sure you use the appropriate weight carbine buffer for your rifle to eject at 3:00-4:00.

• The KP-15 is compatible with 9mm blowback systems with a 5.4oz carbine buffer minimum. Use heavier buffers as long as your gun can cycle reliably. Failure to use this minimum buffer weight can damage the lower.

• Big Bores: .458 SOCOM, .50 Beowulf, and. 50 BMG: We will never test these calibers enough to guarantee function and durability over time; use at your own risk.

Assembly Notes for Gunsmiths and Armorers

Fire Control/Safety Selector Installation.

• The KP-15 can work with traditional selectors and aftermarket selectors. Installing them is easy. Getting them out usually becomes a Gunsmithing operation that sacrifices the selector in the process.

• We recommend the use of our Optimized Mil-Spec Selector (Part Number 1-61-02-003) or Optimized Ambi 90/45 Degree Selectors (Wedge 1-61-02-004 or Bar 1-61-02-005) if you want to be able to get your selector back out of the lower easily without damaging it.

• If all you ever intend to use is Mil-Spec fire control, you can install a normal selector and remove the fire control group for cleaning and maintenance without ever removing the selector.

Fire Control Assembly: General Order of Operations

1) Use the supplied KP-15 Selector Detent. This detent is the same diameter as a traditional selector detent without the rim on the bottom. Detents are available for sale from KE Arms should you lose yours. (Part #1-61-02-006)

2) The selector spring and detent hole is drilled by KE Arms to 0.128” Diameter. This dimension is for your reference should the hole be obstructed with plastic flash during assembly.

3) Place whatever trigger you intend to install in the lower first, but do not install the trigger pin yet.

4) Load the selector spring through the top of the receiver, then load the detent.

5) Insert the selector from the left side and use a punch or other tool to push the detent down into place as you slide the selector over it.

6) Install the trigger pin, then install the hammer/hammer pin.


Magazine Catch/Bolt Catch Installation

1) Install the magazine catch prior to installing the bolt catch. Reversing this order makes the magazine catch much harder to install.

2) The bolt catch plunger should sit roughly even with outer surface of the lower. The hole for the plunger and spring is reamed with a #29 drill. Should you experience plastic flash that was missed in the manufacturing process in this area, spin the drill bit by hand to remove the flash in the hole.

3) Install the bolt catch using a roll pin driver punch only. DO NOT Use Pliers to squeeze the roll pin in. Doing so will damage the lower.

Buffer Detent Installation

• The buffer detent is held in place with a 5/64 x1” Roll Pin

• Get the roll pin started by hammering it part of the way in

• Insert the buffer detent and spring

• Drive the roll pin in the rest of the way with a hammer and punch while holding the detent down.


• The buttplate is held on with a ¼-20 x1” Screw (top) and a 10-32 x 1” Screw (bottom)

• A1 and A2 Buttplates can work with the KP-15 but some fitting may be required

• Look for more buttplate options on in the future.

Further technical assistance can be had by e-mailing

Replacement parts and accessories can be ordered at

*Match Trigger Compatibility.

The front lower portion of the KP-15 fire control area has a radius. This is a fact of plastic design for mold release and strength. Some cassette style triggers with large housings that fill the entire fire control group may not fit. Do not force a cassette trigger into place; you may damage your receiver doing so.

Known Compatible Match Triggers
KE Arms SLT-1
KE Arms SLT-2

Fits But needs new hardware:
Rise Armament RA-535 Fits into the fire control pocket, but will need a longer captured hammer pin.

Known Incompatible Triggers
Triggertech- Does not fit in fire control pocket; holes do not line up due to housing size.
CMC- Does not fit in fire control pocket; holes do not line up due to housing size.