Gale McMillan once said that a perfect barrel doesn't need "outside assistance". Since most of us don't spend the money for that sort of barrel, we resort to various tricks. The Browning Boss is one of them.
My trick is to free-float the barrel, and then install a shim out at the front of the forearm. I use about a five-pound pull to separate barrel and stock to allow insertion. I use kitchen wax paper, as the heat of firing makes the wax melt just a tad and it sticks in place.
A barrel behaves as a spring, and my shim--or a Boss--acts as does a shock absorber on a car. It makes the vibrations uniform from shot to shot, and generally improves group size.
Even so, it is still common that different loads hit at slightly different points of aim. The difference is more often vertical than horizontal, however.
I pick a load for hunting season and stick with it. If it's different from my other loads, I figure it's easy enough to change my sight-in back to what it was before. Heck, it's an excuse to shoot.
Regards,
Art