If it was me and the gun was to be a high end custom with quarter rib etc then I would want a 505 Gibbs.

On the other hand if the gun is to be at the low end and a play thing and mucking about with loads etc. then I would do 500 A2

If the gun is to be a real top end custom job then I agree with 500 Grains that a 505 will have a much better resale value. If the gun is to be an ordinary rifle (like a converted CZ) then I think the 500 A2 would have the better resale value.

Mike