The .450/400 in a Ruger No 1 has indeed been a LOT of fun

As you say, a very flexible medium bore with cheap 41 cal 210gr jacketed pistol bullets for plinking at ~1800fps, a relatively flatter shooting 300gr spire point for medium game at ~2650fps and a 400gr RNSN at ~2200fps for heavy game.

The biggest problem is getting even two loads to print reasonably close together... my 400gr reloads print one foot higher than the factory Hornady 'Dangerous Game' 400gr loads!
I'll try 85gr RL-15 behind the 300gr Hornady and then 85gr 2213SC behind the 400gr Hornady... does the '70% rule' apply?

BTW not impressed with the Hornady 400gr factory ammo, only doing 1827 and 1929fps in my rifle, with incomplete burning... soot and unburned kernels right down the bore

vs ADI 2213SC and Trailboss loads which both burned very cleanly, a nice bright bore after every shot!

I'm keen to order a 400gr paper patched HP mould, and get a soft cast lead option too... much cheaper than Woodleighs at $2+ per shot too