Harv24, I am going to make a guess, as to my Commander. If it has the AR style stock, a castle nut wrench will be needed to loosen the nut, then adjust as necessary. I am not sure this will work with the Concept, but should give a slight adjustment on the commander to either side. If it is the same, any regular AR buttstock castle wrench should work. I have not had mine down, but built many AR style rifles through the years. In a pinch, I have seen people tap the grooves in the nut counter clockwise with a brass punch to loosen it. (I would much rather use a wrench available in most sporting goods stores for about $10) If like an AR where the "false buffer tube" screws into the recess, you should have a slight adjustment, but not much, as there is a detent that sits at "6" o-clock to prevent much adjustment.
google "AR buffer tube assembly" and this should be more clear to you. I hope this helps some!!!! Don't hesitate to ask further if you think we are on the right track!!
Chris
