Does anybody know if similar velocities from different bullet weights are likely to make a double rifle give some degree of regulation? I ask this only because I'd heard that H&H made the different bullet weights shoot together in the .375 flanged magnum before I discovered that the 240 grainers seemed to be loaded down to the same velocity as the heavier ones.

What's this got to do with .416 calibre rifles? Well, I'm wondering if I could get a .500/.416 regulated to the Norma 450 gr slugs and then reload with lighter bullets down to the same velocity.
Then, if I got sick of being thumped around by the heavy bullets, I might still shoot 410 grainers with about the same power as the .450/400.

Can't find Graeme Wright's book at this moment, so can anyone enlighten me on the chances that this might work?