KE Arms KP-15 Monolithic Polymer AR-15 Lower Receiver with SLT Trigger and Ambi Controls – Black

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AT3™ Upper Receiver and SPEAR Handguard Combo

AT3™ Upper Receiver and SPEAR Handguard Combo - Black, 15 inch


AT3™ Upper Receiver and SPEAR Handguard Combo

AT3™ AR 15 Upper Receiver and SPEAR Handguard Combo

AT3™ AR-15 Bolt Carrier Group -  5.56 NATO/.300 Blackout - Black Nitride

AT3™ AR-15 Bolt Carrier Group - 5.56 NATO/.300 Blackout - Black Nitride


AT3™ AR-15 Bolt Carrier Group -  5.56 NATO/.300 Blackout - Black Nitride

AT3™ AR-15 Bolt Carrier Group (BCG) – 5.56 NATO/.300 Blackout – Black Nitride

Innovation, Form, and Function – Monolithic Polymer Lower with Match Trigger

Lighter weight, ambidextrous controls, and a great trigger with enhanced safety features.  This package of the KP-15 polymer lower receiver offers incredible value and usability above and beyond most complete lowers on the market.  The ambidextrous magazine release and safety selector make this lower a great option for left-handed shooters, and the trigger is perfect for just about anyone.  KE Arm’s SLT (Sear Link Technology) trigger has a crisp 4.5 pound pull, short reset, and can function with the safety even then the hammer is down.

And that’s just the improved hardware.  The KP-15 lower itself is made from 30% glass filled nylon, with the receiver, grip, and stock integrated into one durable, lightweight part.  It’s around 8 oz. lighter than a typical complete aluminum receiver, and features none of the weak points typical in a standard lower assembly.  This polymer lower can take a beating, holds up to high rates of fire, and even features a wide magwell for faster reloading.  If you’re not sold yet, check out this full auto torture test and see what the KP-15 can do.


  • 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
  • M-LOK Slots at rear of stock for sling attachment points, or to simply 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
  • Improved grip for comfortable use
  • “Winter” Trigger Guard

Complete SLT-1 Ambi Lower Includes:

  • KE Arms SLT-1 Trigger
  • KP-15 Optimized Ambidextrous Selector
  • KP-15 Long Hammer Pin
  • KE Arms Ambi Mag Catch Assembly
  • Carbine Buffer and Spring
  • Buffer Detent Assembly
  • Bolt Catch Assembly
  • KP-15 Take Down/Pivot Pins
  • A1-Style Solid Buttplate

Technical Information

  • The KP-15 receiver uses a Carbine buffer and spring. Do NOT use anything other than standard buffers and round springs or the JP SCSS in the KP-15.
  • The Take Down and Pivot Pins have the detents built into them; eliminating the spring and detent holes in the lower increases durability.
  • The buffer detent (should you choose to use it) is held in place with a 5/64” Roll Pin
  • The KP-15 is compatible with all Mil-Spec Fire Control Groups
  • The KP-15 is compatible with 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.  Standard selectors can work but removing them can be particularly difficult.   KE Arms recommends the use of the optimized mil-spec selector or optimized ambi selector to make removal easier.  Follow the assembly guide for further instructions.
  • The KP-15 is compatible with standard AR15 uppers in calibers including .223/5.56mm NATO, .300 Blackout, 7.62x39mm, 6.5mm Grendel, 6.8mm SPC, .350 Legend; make sure you use the appropriate weight carbine buffer for your rifle to eject casings 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: .450 Bushmaster, .458 SOCOM, .50 Beowulf, .50 BMG:  KE Arms will never test these calibers enough to guarantee function and durability over time; use at your own risk.


If you intend to have your KP-15 Cerakoted, KE Arms recommends you use We Plead the 2nd.  They are experienced in coating polymer receivers, and have KE Arms’ authorization. The bake should be done at low temperatures (<190 Degrees F), and with an upper in place to prevent warping.

SLT/Ambi KP-15 Instruction Sheet


The KP-15 has a lifetime warranty for normal use.
Sling Attachment points wearing out is not grounds for a receiver replacement.
If the receiver breaks through misuse or neglect, KE Arms will replace it ONCE for $65.00.

Structural modifications including 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 your lower, you are legally the manufacturer and KE Arms cannot service or support it as easily.  Should your receiver require warranty replacement, KE Arms can only replace it with a Title I receiver, and they are not responsible for tax stamps or NFA fees.

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.

Have Questions About this Product?

The AT3 Tactical store has a 90 day no-hassle return policy for products in good condition. You can view the full details of our return policy here.

If you encounter an issue or defect with a product after 90 days of your purchase, you can refer to the manufacturer for a warranty claim. Their policies are below.

KE Arms Warranty

Subject to terms, conditions, and limitations outlined below, KE Arms firearms and products carry a 100% satisfaction guarantee against defects in original materials and workmanship for a period of one (1) year from the date of their original purchase by the initial consumer. This warranty is valid only for products purchased and used in the United States of America.

Limitations Of Warranty

  • The warranty will be void if any of the following occur:
  • The instructions in the included manual are not followed
  • Your KE Arms firearm or any of its parts are altered or modified from their original state
  • Damage is caused by misuse, abuse, or improper maintenance
  • Reloaded, remanufactured, or hand-loaded ammunition or ammunition of a different caliber than your KE Arms firearm is used.


  • Any unused, unopened item may be returned for store credit equal to 100% of the purchase price.
  • Any unused, unopened item may be returned for cash, minus a 30% restocking fee.
  • Returns are not allowed on firearms or parts that have been fired or used in any way. (This is determined at the discretion of KE Arms)

Disclaimer: Manufacturer’s warranty is subject to change without prior notice.