pabuck With the 284 mags so hard to find IF you have some mechanical skill buy a 308 based mag and open up the feed lips. There is only a .141 differnece in case width and the same lenght. Atleast its worth try'n. Might be all thats needed is the feed lips to be bent up a couple ths, or ground back .07 on each side to raise the cartidge enought to feed.
Know that it is done with rifles rechamber from 308 based cartidge to 284 based cartidges. - http://www.6mmbr.com/gunweek095.html