Hi Ted, Ill take a quick stab at this. Chrome Carrier: Less friction and easier to keep clean Tactical Latch - Essentially has large pad on the charging handle latch. Ill attach picture from an AR-15 version Gas block - Quad rail would be used to attach accessories like lights and lasers. Aluminum is typically the cheapest option and also the lightest. Down side is with use after thousands of rounds the aluminum will bet eaten up by the gases quicker then a heavier stainless block. JP blocks - JP has many options, from low profile, single picatinny to adjustable gas. It really depends on what you want to do and which you are curious about. Tell us more about what your configuring and maybe we can offer more specific advice. Thanks for joining