I've had both .404J and .375 H&H rifles. Here's a link to my .404J build, which I posted earlier. After shoulder surgery, I sold the .404, kept the .375, also a SS M-70.

http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/7846376/3

A good bit of .404J info.

DF