Sorry about being slow, I am off line after noon CST. Wolfe Publishing has a BIG book of Handloader reprint articles available. It covers a LOT of cartridges. Go to their web site or call them and find it. Bob Hagel has an very thorough article re. Mashburn history/loading in it. Retumbo and RL-25 powders weren't available when Hagel did his article and I believe they are really execelent in this application. I use RL-25. As a reference, I use a current Hornady manual and 7 Roy data for loading inspiration.
As Bob says the Mashburn & Dakohata are about equal. Serious horse power is a right sized package
I suspect not many 'smiths have Mashburn reamers on hand anymore. I called JGS and they gave me a list of people that had bought that reamer and I rented it from a fellow in Oregon. You might call Dave Kiff at Pacific Tool or maybe Fred Zieglen for reamer rental/sources.
The easiest way to make brass is to use a RCBS form die set and start with .300 Win. Mag. I prefer Federal but anyones will do. The original parent case was .300 H&H.
