6.5 GRENDEL UPPER

Thinking about building one how would you go with this? 20 inch barrel. I like Alexander Arms but they only do the complete upper from what I can find, or would that be the best way?
other options are
bwh
red x
shilen
lothar wather
satern
jp

I like to shoot long range for fun but not comp and will be using it for hogs and deer along with varmints.

I have an Alexander arms upper and a Lothar Walther barrel.

Robby

I have been looking there as well as other places. It is hard to decide who
makes the higher quality