Most of that will depend on what individual parts parts or kits you buy. Basically:
- Builder set if you go that route from Aero, it will have assembled upper receiver, stripped lower, a barrel but, and hand guard. You can also piece together an upper, lower, upper parts and hand guard.
- A lower parts kit. Some come with a trigger & grip, some do not. You can also pick and choose individual parts.
- Barrel and bolt. Some barrels will come with a head spaced bolt, some don’t. If it doesn’t you should confirm head spacing with the bolt you purchase.
- Gas block and gas tube. Make sure you get a roll pin if one of those parts does not come with it.
- Bolt carrier or complete bolt carrier group, depending on if you got a bolt with the barrel. Also depending on how you buy this you may have to get a firing pin, cam pin, retaining pin, gas key...I may have missed something.
- Charging handle.
- Furniture can come as a set, or bought in pieces.
- Maybe a flash hider and crush washer, thread protector, brake, maybe not. Depends on your barrel choice and preference.
- Buffer and spring.
I think that’s it. You can also buy a kit that has everything, but to me that defeats the purpose of building one.
