I'm glad your pleased with Trail Boss in the 577/450, but you should be aware that it has been shown to produce irregular and significant pressure spikes in the 577/450 by those with access to proper tools for measuring. Looking for signs of high pressure in this cartridge is a bit misleading, since the MH is a 26,000 psi rifle and high pressure signs wouldn't occur until almost twice that level. While it is true that MH rifles were converted in mass to .303, it is also true that the much smaller base of the .303 cartridge produces much less bolt thrust despite its much higher pressure. Needless to say, the Gahendra is a far weaker action where any pressures above BP levels should be avoided. Unless you have access to the proper tools for measuring pressures, I would never advise anyone on using Trail Boss in such cavernous cases as the 577/450.
Rich in West Virginia, savoring life one cartridge at a time.