I recall reading something similar. The idea was a, well, mini m14, but it turns out you need all that gun for a .308. Seems kind of obvious - I think they'd have made the M14 smaller if they could. The article (in some supermarket gun rag I can't remember) said they already had a bunch of the barrels made and decided to use them in the mini 30. And that they developed a chamber with an aggressive conical reduction in diameter at the front to make it work with the bigger bullets. Like a super throat. No idea if any of that's true. But mine was super inaccurate, so it wouldn't surprise me. The trigger mechanism also fell out when you fired it. This was around 1993.If memory serves, Ruger was advertising the Ruger XGI in the mid1980s as a follow on to the Mini-14 and it was going to be in 7.62X51/.308Win. I remember seeing ads for it in some gun rags (magazines) circa 1985. Then it quietly disappeared. I heard rumors decades later that they could not get it to shoot properly and abandoned the project. Seeing as the original Mini-14 was not the paragon of precision, I can only imagine how bad the XGI must have been for Ruger to dump it.
Edited to add: Well, wouldn't you know it, Wikipedia has a page for the XGI:
Ruger XGI - Wikipedia
en.wikipedia.org