20" upper vs 18" upper

[Jimla]

You might want to check this guy out, if I were to buy a complete upper he's the guy I'd buy it from, have heard nothing but good reports about him. Also he's in your budget.

https://www.grendelhunter.com/

I was between AT3Tactical and Grendelhunter, I ask both companies about there accuracy guarantees and AT3Tactical was the clear winner.

I would stay clear of this grendelhunter, below is the reply I got about accuracy guarantee.

"Technically, we don't have an MOA guarantee. Pretty much everyone does it these days, including companies that use low quality barrels, so it feels like a bit of a gimmick. That being said, once in a while a customer will contact us with accuracy concerns. After looking at obvious things like the scope and mount, we generally just send a return shipping label so I can go and shoot it myself. If there's a problem, we make it right. But to be honest, it's almost always a case of user error. "