I will soon be the proud owner of a custom-built 300 WSM. The gun is sure to be capable of 1/2 MOA groups with good loads.

Now, where can I find data on working up these good loads? I've found a recipe or two, but no general information on the round (such as max case length, trim to length, best powders, etc.).

Speaking of powders, I've been told to forget my normal magnum-type loads where I utilize slow buring powders like H 4831. They said faster powders (like Reloader 19) work best because of the case shape. Is this true?

What primers work best?

I'm a fan of 180-grain Speer Grand Slam bullets in my 300 mags. Anyone used this bullet in the WSM?

Any help in getting started in this new caliber will be greatly appreciated.

By the way, I'm new to this forum. I've spent the last couple of years on Huntingbbs forum. It's a good one, too, but no one has any WSM experience there.

The "gun" magazines have been full of loads for the WSM...American Rifleman, Rifle, HandLoader, etc etc. plus I would expect the new Nosler manual due out around Christmas to have loads.....I would do a web search.

The Hodgdon website has significant data for what you are seeking.

The new Barnes manual has data for the 300 WSM. They get some pretty decent velocities with the XLC's.