Well, a few years later then expected, but it seem Shell Shock rifle cases are now a reality, and for sale on their website. Starting with .300 BLK, hopefully more to follow.

A look at their latest, 'step down' profile stainless steel base:

https://www.shellshocktechnologies.com/wp16/wp-content/uploads/2023/02/300-BLK-cases-close-up-scaled.jpg

I'll try and find out the case weight. Curious what savings they are able to accomplish given that the base is Stainless Steel. 

I used to really like the idea of the Shell Shock case.  However I see a huge problem with them now.  Even in brass cartridges, one occasionally sees the rim sheered off by the extractor, which causes a catastrophic failure of the weapon.... no matter the grade of aluminum it is still going to be super soft compared to brass or steel, and so I really would not trust an aluminum base case in a military setting.  I think ultimately, old school mild steel cases are tough to beat in terms of relative cost, durability and weight. 

Well it seem SS only uses aluminum for its pistol calibers; its rifle cases seem to use a stainless steel base.