Great gun. I run a Rob Roberts .660 in lower barrel, my Nikon Red Dot is sighted in with this barrel. I use the spreader in the Top barrel for close range, and if I run and gun, I'll put a Browning Full Strut Choke in the upper for 2 long range options. My barrels POA is very close, within a half inch of the sighted lower barrel. For the sling, I put a stud in the rear stock, drilled and threaded it in just like wood. I used a barrel clamp stud for the upper sling stud. Great gun, you'll love it. It shoots all loads very well, I use Federal Heavyweight 7's most of the time, Longbeard 6's too.