Bedding an AR?

[A5BLASTER]

What I have learned is for the best accuracy potential from a barrel and upper reciver is you want a barrel and upper reciver that you have to freeze the barrel and heat the upper in the oven to beable to install the barrel and upper together. That way when the barrel warms and the upper cools the upper shrinkes and the barrel will swell and they will have the tightest fit possible.