A couple years ago I ran across a new bolt in a drawer in the garage. Forgot I had it. Then, at the bottom of the drawer I found a quad rail I'd bought for my nephew that he decided he didn't want. Well, darn. All I needed was an upper, lower, lower parts kit and barrel, some sights and a sling.
It turned into a whole carbine in a few weeks.
Got a bolt, upper, lower, lower parts kit in the shed right now (was supposed to be a project for a youngster who has decided to be undeserving of a new AR15 carbine and ammo). Sooner or later, I'll have to finish it up for my own. Unused parts are just not right. I had thought of holding on to them in case my youngest son and his new wife gave us a grandchild, but that could be so many years from now (till the kid was old enough) that I might not even be here to build the a carbine.
Oh, back to the tool. Does that guide rail unbolt from the rod? If so, could you take it off, sand a little off the side (if you can determine which side is dragging - or is it both sides?) and reinstall it?
It's either too wide and dragging on both sides. Or the upper is too tight (maybe out of spec?) Or maybe the barrel is slightly canted one way or the other resulting in the rod being twisted to one side, or the other, as the end of the rod engages the barrel extension lugs as it reaches/mates with them. Hard to tell from here.
Good luck with it.