M4 Carbine Schematic | military - Pinterest A place to buy parts, rifle kits, complete upper receivers and lower receivers. Such as lower parts kits, jigs and other shooting and survival gear. Breakdown of the AR 15 Once again, there has been another mass shooting involving a gun that looks like an (it’s technically a Sig Sauer MCX, which may or M4 | Top Rated Supplier of Firearm Reloading Equipment Schematic ID# 916. Click on a red number to view more information on that item and to add that factory part to your shopping cart. Select "SKU Listing" to see all stock numbers for this schematic.