Dec 23, 2025

US12504247 - Modular firearm lower receiver assembly for rapid conversion of AR-15 type firearms to a bullpup configuration and method of assembly thereof

The present invention is a modular firearm lower receiver assembly for rapid conversion of conventionally configured modular firearms to a bullpup configuration and the method of assembly thereof. The preferred embodiment of the present invention is intended for designed use with modular firearms in the family AR-15 Type Firearms and enables a rapid conversion of a wide array of conventionally configured AR-15 Type Firearm to and a bullpup configuration. Such rapid conversion, which can generally be performed in a matter of seconds without any tools, is accomplished by decoupling and detaching the two captured receiver pins on the lower receiver of the conventionally configured AR-15 Type Firearm, removing the upper receiver assembly therefrom, and recoupling such upper receiver assembly to the present invention using two identically located receiver pins on the present invention. The present invention is universally applicable to AR-15 Type firearms of several different calibers and having an array of differences with respect to the lower receiver, upper receiver, handguard, bolt carrier group, or gas systems employed therein.

Inventors: Michael C. Hamersley
Filing date: 2024-07-08

firearmmodularbullpupar15

The invention provides a modular lower receiver assembly that allows for the quick conversion of AR-15 type firearms to a bullpup configuration without the need for tools. This conversion can be completed in seconds by detaching and reattaching the upper receiver assembly using specially designed receiver pins.

Claim 1

1 . A method of converting a rifle assembly to a bull-pup configuration, comprising: a lower receiver; interlocking a lower receiver bull-pup interface having a pistol grip and trigger guard to an upper receiver assembly of a firearm, the lower receiver bull-pup interface having a forward end, a rear end, and a channel therebetween for accepting the upper receiver assembly, the rear end of the bull-pup interface having opposing upperwardly facing hook portions configured to overlap pivot pin apertures of the lower receiver and to accept a pivot pin; coupling a trigger relocation assembly between a trigger of the lower receiver and a trigger of the bull-pup interface; and interfacing a recoil buffer and recoil spring of the lower receiver to the firearm. a lower receiver; interlocking a lower receiver bull-pup interface having a pistol grip and trigger guard to an upper receiver assembly of a firearm, the lower receiver bull-pup interface having a forward end, a rear end, and a channel therebetween for accepting the upper receiver assembly, the rear end of the bull-pup interface having opposing upperwardly facing hook portions configured to overlap pivot pin apertures of the lower receiver and to accept a pivot pin; coupling a trigger relocation assembly between a trigger of the lower receiver and a trigger of the bull-pup interface; and interfacing a recoil buffer and recoil spring of the lower receiver to the firearm.

Google Patents

https://patents.google.com/patent/US12504247

USPTO PDF

https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/12504247