budget

So, I'm looking to build a custom AR Pistol. It's kind of an odd project, and it's hard to find out if the parts that I am looking at are compatible. This here is the type of build I am going for. Silly? Yes Impractical? Yes But it was extremely fun to shoot my friends build. I am looking to...

Any recommendations for a budget 20" upper, or just a good company to use? Just finished my first lower build. There are a lot out there and I'd love your input.