The main problem with the QLA is that it is not centered on the bore it is centered on the outside of the barrel. Some get lucky and have the bore centered on the barrel so the QLA is centered on the bore as well, most aren't that lucky. The inaccuracies show up the most when shooting full bore conicals.
TC has claimed that the reason their rifles don't shoot conicals accurately is not the QLA but it is because they have too fast a twist which is contrary to logical thinking. Off the top of my head I can think of three members of these forums who have cut the QLA off, recrowned their barrels and gotten accuracy shooting conicals.