“I can tell you now, putting together an AR-10 is a bit more challenging than a Mil-Spec AR-10. What I have learned from this exercise is that the lower and and upper needs to be from the same company and series. I.e. if you but a PSA lower, then you need a PSA Upper. If you buy an Aero A5 lower, you need an Aero M5 upper. BEFORE making your purchase, you need to see if ALL of the parts are in stock because universal parts rarely apply. Things that are universal with the AERO M5 are the trigger ( you can install Milspec or whatever you want. Mag release is MilSpec and the safety. Outside of that, be VERY Careful with the pivot and take down pin. The pivot pin especially. Otherwise you will wind up with someting too short or require a punch to disengage the front pivot pin. I do think that is a flaw in the design of the UPPER. I have seen other AR10's make the same mistake. The ports that hold the pivot pin is thick, so the pin doesn't stick out enough to push with your fingers to break tension so you can pull the pivot pin out. AR15 pivot and take down pins do not work - they are too short. The spring and dentent for the pivot and take down was more challenging to put in on this build. The take down pin was the most challenging. Typically with an AR15, you insert the spring in the back where the buffer tube screws in. The Aero M5 uses a port where the AR grip goes. The challenge is a standard grip only has one port in it and that port is for the spring and detent for the safety. I messed up my spring for the take down pin trying to cram it in the port the Aero M5 has for it being that the grip had no relief for the spring. With patiences I got it to seed, but when you take the grip off, KNOW that you will have two springs and two detents to contend with that belong to the safety and the rear take down. I don't think that ANY AR-10 upper has it completely right. But assembly aside, the upper is solid. Also note, that the Aero M5 is "enhanced" and therefore requires the "enhanced" handguard. If I went with the nonenhanced model, then I could've had more options on what to use. There are limited options for the Aero M5 handguards. Specifically with them being in stock and can be pricey compared to other systems. Ferrari life Ferrari problems. I gave it 5 stars because the upper still very well made and although I ran into limits, it doesn't mean someone with better tools, or a deeper wallet would run in the same hurdles. If you're trying to nickle and dime the build, these are the issues you would run into, but that wouldn't neccesarily change by buying another brand. I bought this upper through Arm or Ally at a really good price and I do not regret it at all. I would've bought 2 or 3 if I could because the deal was so good, and that is even with the challenges of the take down/pivot pin and handgaurd.”
