NOTE: The following data exceeds SAAMI specifications and can be dangerous to use in certain rifles.

Sierra Match King 77gr BTHP
25.3gr Hodgdon Varget
LC Brass
Winchester SR Primer

Developed in a White Oak Armament 18" SPR configuration with a Wylde chamber.

Note: At the time, I was using Winchester SR primers. I would recommend Remington or CCI instead.

Any load that will give you Mk262 performance will exceed SAAMI specifications for .223. Thus, you're not going to find any published commercial data that will meet Mk262 velocities.

You shouldn't use anyone's Mk262 'recipe' straight up.

If you want to make your own Mk262 clone ammo, you NEED to get a chronograph and work up the load appropriately. Don't kid yourself thinking you can just use someone else's recipe or the commercial data and guestimate the proper load to meet a specific velocity. The Mk262 pressures/velocities are pretty hot and you're going to need to carefully find the right load for your specific rifle. And when you do find the correct load for your specific rifle, you need to reconfirm the load every time you go to a new lot # in bullets, powder, primers, or cases.
http://www.223reloads.com/home/223-5...uplicatingnato