There's not a ton written about this that I can find, but cracks are appearing in the US military's plan to replace the M4 with a heavier battle rifle designed to defeat body armor. Sig Sauer, which also holds contracts for the current generation pistol and LMG, won a contract last year to also provide the US military with a new rifle. This rifle is to be called the XM7. The civilian equivalent is the Sig Spear. Calling this thing an assault rifle is a bit of a stretch, as it is very heavy and uses heavy ammunition. It turns out that the rifle is failing to penetrate modern body armor without the use of tungsten bullets. Also its reliability is questionable.
It is interesting that in the last 5 or 6 years Sig has secured contracts for basically all the new light arms. I'm not a big enough gun nut to have an opinion on whether the contracts were deserved based on the relative quality of their submissions.
Me neither, but even with my base knowledge it sounds like the US DOD wanted to dump money into manufacturing a whole new ammunition type and gun, and the Sig contracts allowed them to fulfill that role with the 6.8x51mm round.
From what I've gathered from gun community scuttlebutt, it's a combination of very aggressively pricing their bids, and being very savvy about navigating and circumventing the testing process. So we're in this place of "maybe Sig's stuff is good? maybe they can actually make enough without cutting corners?"
They're timing this exactly correctly, as the US military is in the long ongoing process of refitting all their equipment after two decades of war on terror shit using tech from the 80s. Stuff like scopes and accessories of course are a huge bonanza, and legitimately a powerful force multiplier. But the actual tech of the shooty bits has plateaued for decades, and we see stuff like the m17 and m5, which are, at best, slightly nicer than what they were previously using.