AR15 primer for beginners. I am the first to admit that its long winded and the author is full of himself, but he does make a few good points.
1) What's on the inside is more important than on the inside. Especially if you want to use it for a defensive role, insist on a carpenter 158 bolt that is INDIVIDUALLY high pressure and magnetic partical tested. The pretty colors on the outside are secondary. Don't believe the hype. How's that saying go? A pig with lipstick...
2) Chrome lining is for durability, the trade of is a smidgen of accuracy. Your call.
3) Q hit it on the head, but I will add that if shoot with one of the newer shooting styles with your support arm extended, you will want to go with a longer forearm.
4) To my knowledge they don't make stamped receivers for ARs. Maybe you have them confused with AKs as those are commonly stamped. The shape is too complex for stamping.