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USC to UMP

Photo Gallery

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Zero Hour Assembly Tips Upper/Lower Assembled
Trigger Housing
Refer to Key Lower Housing collection of setps with photographs.

USC Lower Pristine


Rear View USC Locking Lever with Springs


Locking Lever Removed


Hammer and Sear Set Aside


Hammer with Spring Fixed


Pins Popped from Right to Left


Pre-Trigger and Spring Removal

FBI Trigger Housing Conversion
Refer to Key Lower Housing collection of setps with photographs.
Images Faked Using USC Trigger Housing

Pin Trigger and Spring Note use of probe.


Hammer Springs Relaxed Forward of Stud.


Sear and Spring Installer. Use gentle pressure on sear/spring and pull/push probe to seat.


Install Hammer/Spring Relaxed. Pin with probe. Note relaxed position of hammer spring on wall infront of stud.


Pin Hammer Pushing Probe Out of Housing. Maintain relaxed hammer spring.


Hammer Pin Needs to Be Flush. Gently push or hammer flush


Zoom-In to See Hammer Spring in Relaxed Positon. Note Hammer pin is flush to housing. Now ready to pre-load Hammer Spring using thumb nail to move around to back of stud.


Zoom-In to See Hammer Spring in Pre-Load state. Hammer is held in full travel forward position by Pre-Load.


Hammer engaged by Sear. Forcefully place palm over front of Hammer before releasing Trigger to PREVENT DAMAGE to Housing.

Mag Well Pre-Cut



Ejection Well



Hinge Pin Ejector Side



Hinge Pin Cocking Lever Side




Lower Ready For Final Assembly



Lower Drop Test




Cocking Lever Side



Ejector Side




Foldeed Stock Position




10 Round USC Magazine




10 Round USC Magazine From Lower



Please send comments or questions using e-mail . (Last update: March 21, 2015 tar)