The one QLA that was really off that I have seen would not shoot anything well, it shot sabots in a 6 inch group at 50 yards no matter what was tried. The others shot Thor, FPB and PB into the normal size group for the shooter.
I shot no excuses in one of my QLA TC guns for a hunting trip by using the old cornmeal method[a wad and enough cornmeal to fill the QLA until the bullet exited] and while it had a rainbow trajectory it shot in 2 inches at 100 which I have always considered reasonable for a soft lead bullet.
My reasoning has always been that the powder gases bouncing off the side walls when it can go between the bullet and the QLA is going to mess with the accuracy.
I realize I am probably alone in this line of thought because no one else has ever mentioned it.