IM looking into getting a new upper for my AR. Right now i have a S&W M&P that is all original. The upper on it works great but i want something to go with my current 16" barrel as more of a precision setup. IM lookin at a Giesell trigger but not sure which one yet and want a varmint upper with a 20" barrel. So my question is who makes a good Varmint upper? Ive been looking at the RRA.