Would anyone happen to have some knowledge or info on the 300 Mashburn Super such as what may have been used for the parent case ?
I might acquire a Mod.70 pre-64 in that chambering and I've heard of the 7mm Mashburn but not the 300.
Any info would be greatly appreciated.

kevan - check this out - some data sheets for Mashburn rounds - http://forums.accuratereloadin.../9411043/m/142108376 - may have some of the data your looking for.