Paul,
The .505 is fine, but I haven't been shooting it since my shoulder surgery last year. I just started shooting last time in with my 9.3x62 and that went fine. I'm gonna ease on up through the .416 and .450No2's before I start the big guy again.
I have some great loads to try with the 570grn Barnes X bullets that I got from Nickudu.
We'll have to get together to shoot when the weather warms up some.
Ron