HK21 Semi-Auto Belt-Fed Clone (.308 / 7.62 NATO) – Portuguese Feed Mechanism | German HK Barrel | Full Auto Ready Sear Host | Built by Full Auto LLC | Jacksonville, FL
Description
Offered for sale by Full Auto LLC (Florida FFL/SOT) is a newly built HK21 semi-automatic belt-fed clone chambered in .308 / 7.62 NATO. This rifle was professionally assembled by Full Auto LLC using a Portuguese HK21 parts kit featuring an original Portuguese belt-feed mechanism and fitted with a German HK barrel, delivering an authentic HK21 configuration in a semi-automatic platform.
Built on a U.S.-made semi-auto receiver and test fired only, this example represents a rare opportunity to acquire a properly configured HK21-style belt-fed rifle combining military surplus components with a newly built receiver.
This firearm is configured as a semi-automatic HK21 sear host. It is full-auto ready and designed to accept a properly registered HK auto sear installed in a clipped and pinned lower, where legally permitted. Without a registered sear, the firearm functions as a semi-automatic rifle only. All NFA rules and applicable laws apply.
The HK21 is one of Heckler & Koch’s most iconic belt-fed systems, known for its roller-delayed blowback design, reliability, and distinctive military heritage. Semi-auto HK21 builds are rarely encountered due to the complexity of the platform and limited availability of quality parts kits, making well-executed builds highly desirable among collectors and HK enthusiasts.
Located in Jacksonville, Florida.
👉 For more information or to purchase, email:
mailto:myfullautollc@gmail.com
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Key Details
•Model: HK21 Semi-Auto Belt-Fed Clone
•Builder: Full Auto LLC
•Configuration: Semi-Automatic (Non-NFA)
•Sear Host: Yes, full-auto ready with registered HK sear (not included)
•Caliber: .308 / 7.62 NATO
•Receiver: U.S.-made semi-auto receiver
•Feed Mechanism: Original Portuguese HK21 belt-feed system
•Barrel: German HK barrel
•Parts Kit: Portuguese HK21 surplus components
•Operating System: Roller-delayed blowback (HK pattern)
•Condition: New build from surplus kit, test fired only
•Includes: Bipod
•Location: Jacksonville, Florida
•Seller: Full Auto LLC – Florida FFL / SOT
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Overview
The HK21 platform remains one of the most distinctive belt-fed firearm systems developed by Heckler & Koch. Properly configured sear hosts are especially desirable among HK collectors and transferable sear owners, allowing modular use across multiple HK-pattern platforms. This example combines authentic military components with a modern semi-auto receiver, offering flexibility for collectors and enthusiasts.
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