Get the pinned WOA with the 1/7 Wilson. If you are serious about highpower, you find a way to justify the spendier barrels or you'll stick with the Wilson 1/7, as you progress. If you're going to shoot irons, you might as well shoot out of Holliger's sights. Dead nuts repeatablity throughout the elvation and windage range. Positive clicks without backlash or binding. The removable hooded sights are slick.
So yes, spend the few extra bucks and get a pinned rear sight.
The WOA 1/7 has a Wylde chamber and is chambered by Frank White of CLE. All for a little over $200 for a replacement barrell! What the hell are wondering about? John's uppers shoot great.
My shooting partner has the PacNor 6.5 with the 223 Holliger chamber (looong throat). It shoots great and is wonderful piece of work. You only need the 6.5 if you want to shoot 90SMKs or JLKs.
I may be mistaken, but SabreDefence is known for their chromed barrels, not match barrels.