Does anyone use the 300gr .411 bullets in the 450/400? Does anyone have any accurate loads for a Ruger#1 in 450/400?

If you mean the Hornady's made for the 405? I do use them in my Ruger #1. I have used both the flat point and the pointed ones. I only wanted to duplicate the 405 velocity at 2200 fps so I don't have any screamers. I wanted a light load. I use 65 grains of IMR 4320 for 2225 fps. Federal mag primer. Nice, relatively light load. Very accurate in my #1. I also use that load in my 400 Jeffrey Mauser (.410 groove dia). Because the 400 grain bullets kick the snot of you .

Yes. Also any good 450/400 400 grain loads? No worries I am use to getting the snot kicked out of me.

This Mauser with 400 grainers is brutal on the face due to the stock drop; nothing like the mild recoil of the #1. The #1 has a very straight stock so the recoil is not that bad in this caliber, and the K is so heavy that there is hardly any recoil at all. For 400 grainers in my Ruger and Krieghoff, I use 74 grains of 4350 which regulates perfectly. There are tons of loads for the 450-400 out there.