The distinction is tougher to make,beings I don't form via 300H&H parent hulls. The 8mm Rem mag is purty "improved" outta da gate and that transformation is very modest,when fireforming in the Super chamber.
I reckon I prolly have some virgin 375H&H hulls to compare and some 7STW stuff kicking around too and could do a modest extrapolation via those means.
The 300H&H is easily the schittiest full length H&H hull of All Time...........................