just picked up a Colt Match HBAR 1 in 7 A2 upper it’s a post ban with a non-threaded bbl… If i have it threaded and install a flash hider or muzzle break will i lose accuracy by doing this the bbl has a nice target crown??? Looking at a Magpul PRS Stock sense this is a A2 upper I’ll be useing a ARMS #2 Carry Handle mount for my scope… Will the PRS Stock adjust up enough to give me a good view through the scope…
if you take it to a quality place that can do barrels, you should not loose a thing.
Velcro
+1 if done correctly it wont hurt 
I did the same to my Colt HBAR a few years ago…with the FH I had to zero the weapon again (only by a few clicks) but the groups were the same
send it to have the work done???
ADCO is the place to go IMO.