You can't technically build one from a separate upper and lower. You have to buy it complete. I bought the pistol with a standard gas impingement 10" upper and a no frills Mega Arms lower. I rebuilt the lower with better guts and put an Adams Arms gas piston 7 3/4" upper. Added the Primary Arms micro red dot, MBus flip up co-witness sights and the CRD break. The plan was to use it for HD, but it's way too loud and belches way too much fire for night time encounters. That is and no photo shop picture. It's a single frame from slow motion video.
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