Clays is very fast and not a great choice for the 10mm. Spend a few bucks and get a slower powder better suited for the 10mm.
Follow your manuals and NOT what you have heard.
BTW, what manuals do you have?
Give a man a fish and he eats for a day. Give a man a welfare check, a forty ounce malt liquor, a crack pipe and some Air Jordan's and he votes Democrat for a lifetime.