Uppers are SO easy to build...
Got an Aero receiver, Green Mountain 6.8 SPC barrel, Matrix 13" rail, and standard 6.8 nitrite bolt. Took under 2 hours to put together with basic tools (first time). Gas tubes/blocks are cheap if you shop around (some barrels also come with the gas block). Same with the riser for the scope or red dot- Aim sports has one for $30- its SOLID. My standard "buffer tube spring" works between both my 223 and 6.8 SPC upper fine too.
I admit I tweak ALL my guns (mostly triggers) but not a gun smith. Built both uppers to use with the better Palmetto lower (always on sale for $149 shipped). I don't like the standard Palmetto barrels- get an upgrade (they USED to sell uppers with an FN barrel, but haven't seen that option for years now- the standard line has cheap barrels... definitely upgrade the barrel!)
Both guns I built shoot MOA or better... and you don't need a barrel nut wrench if using the Matrix rails (which come with a great one you can put on with a standard crescent wrench). These Matrix rails are UNDER $80 shipped (*and are an OEM for Ruger's ARs). Their receivers are also good too. But do get a set of $30 blocks to hold the receiver when torquing the barrel.
Cost to DYI the first time is about the same as a mid-range upper pre-built, but upper #2 will be way cheaper with the blocks (and experience from build #1).
