KE Arms KP-9 Complete Polymer Lower Receiver with Mil-Spec Trigger – 9mm

SKU: 1-61-03-002

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AT3 Tactical 9mm Bolt Carrier Group - Nitride


Highly Durable & Cost-Effective 9mm Polymer Lower with Mil-Spec FCG, Buffer, & Spring

The KE Arms KP-9 is a pistol caliber lower receiver designed with an integrated buttstock, buffer tube, pistol grip, and trigger guard all in one piece. It combines the features of the highly successful KP-15 Monolithic Polymer Receiver and the billet KE-9 Glock magazine-compatible lower to make a lightweight, highly durable, and cost-effective pistol caliber carbine lower.

The KP-9 is built to accept 9mm Glock 17 and Glock 19 pattern magazines, and precision-machined to Mil-spec standards making it compatible with most Mil-spec 9mm upper assemblies.

Lightweight & Improved

The KE Arms KP-9 Polymer Lower Receiver is made from injection-molded 30% glass-filled nylon polymer giving it a much lighter weight compared to similarly configured lower receivers. It also features a flared magwell for faster magazine reloads, a winter-glove ready trigger guard, and an improved pistol grip with an anti-slip texture for enhanced ergonomics and comfort.

NOTE: This lower is the Mil-Spec FCG version of KP-9 that comes with a Mil-Spec Fire Control Group, Optimized Ambi Safety, 9mm Heavy Buffer, and Spring

Mil-Spec FCG Lowers Include:

  • Mil-Spec Fire Control FCG
  • Optimized Ambi Selector
  • 5.4oz 9mm Heavy Buffer and Spring
  • Bolt Catch Assembly*
  • Pivot and Take Down Pins
  • KP-9 Selector Detent
  • Buttplate
  • 5/64″ Roll Pin to Retain Buffer Detent
  • Ambi Glock Magazine Catch Assembly
  • Adjustable 9mm Steel Ejector

Technical Information:

  • The KP-9 receiver uses a Carbine buffer and spring. Do NOT use anything other than standard 9mm carbine buffers and round springs or the JP SCSS in the KP-9.
  • 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-9 is compatible with all Mil-Spec Fire Control Groups
  • The KP-9 is compatible with cassette-style match triggers including the KE Arms 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-9 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.   We recommend the use of our optimized mil-spec selector or optimized ambi selector to make removal easier.  Follow our assembly guide for further instructions.
  • The KP-9 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.
  • CMMG Radial Delayed Blowback Uppers will need modifications to the ejector to work.
  • The KP-9 DOES NOT have Last Round Bolt Hold Open (LRBHO) unless you use an upper with a linkage system built in to accommodate it. The AR15 magazine catch can be used to manually lock the bolt back, but Glock magazine followers DO NOT interface with it. If you want LRBHO with this lower, check out the Aero Precision EPC-9 upper receiver, which contains the needed linkage system.


  • Lighter weight compared to similarly configured receivers
  • Lower cost to similarly configured receivers
  • Compatibility with most common 9mm AR15 uppers and lower parts kits
  • Compatible with Glock 17 and 19 Magazines
  • 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 the 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
  • Improved grip for comfortable use
  • “Winter” Trigger Guard

DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.


Caliber9x19mm Parabellum
Receiver MaterialPolymer
Firearm TypeLower Receiver
Weight27 ounces

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.