The src has moved since 1.2.1, but the ebuild wasn’t updated to reflect that when it was bumped. The SRC_URI for 1.2.1 was: http://icl.cs.utk.edu/projectsfiles/${PN}/${P}.tar.gz For 1.3.0 it needs to be: http://icl.cs.utk.edu/projectsfiles/${PN}/pubs/${P}.tar.gz Note the /pubs/ directory.
+ 03 Jan 2013; Sébastien Fabbro <bicatali@gentoo.org> magma-1.3.0.ebuild: + sci-libs/magma: Fixed URL, thanks James Cloos +