Here is how Thompson Center explaines it.,
13: I've heard about T/C's new QLA® Muzzle System. What exactly is it?
T/C's QLA® Muzzle System (Quick, Load, Accurizor) is basicly a built in "false muzzle". Many old time target shooters used to attach a false muzzle to their rifle barrel for loading purposes, to guarantee precise alignment of the projectile during the loading procedure. They would then remove the "false muzzle" prior to shooting. The "false muzzle" also protected the rifling from being damaged or worn during loading. T/C's QLA® Muzzle is built right into the end of the barrel in all of our rifles permanently. It guarantees consistent alignment of your projectile in that its surrounded by steel for 360 degrees prior to being driven down the bore and engraved with the rifling. The projectile can't tilt, and the shape can't be altered (lead is soft) as it is started down the bore. This consistent alignment from shot to shot greatly improves the accuracy potential of the rifle by eliminating one of the variable associated with good accuracy... projectile alignment. T/C's QLA® Muzzle System also makes loading your second shot in the field much easier. You merely drop the projectile in the barrel and go straight to your ramrod, using short strokes. It eliminates the hassle of trying to align the projectile with one hand, and drive it into the rifling with a short starter.