All of Dan's .504 conicals from 500 grains downward in weight are under the 2X caliber limit imposed by some states.

The 445 grain UC Short might also be a good one to check out. Sorry for the blurry pics but Dan's is a family of bullet makers, not photographers. I pieced together a bunch of individual pictures to make this composite of his conicals. He actually has several other offerings now, but I think those shown remain the most commonly used ones. My guess would be that your rifle will easily load the .504 diameter but if you need .503 or even .5035 - he can very likely do either. He would probably make you up a sample order at a reasonable price.