Has SIG made any significant improvements to the 556R?
As a Beta tester of this rifle I was rather disappointed, have they upped their game recently?
The new version is the 556xi, which can be swapped from 5.56 to 7.62x39 to .300 BO, with 16" and 10" barrels available for each. It has several improvements, one of the most significant being an ambi charging handle, also a cheek riser that allows comfortable use of AR-15-height sights and optics, and of course the quick-swap barrels and lowers.
As far as reliability goes, it is too new to really know. Gabe Suarez just released a very positive review of the 7.62x39 version though.
I am strongly considering one of these to fill the role of the AK I sold a couple years ago… if I can come up with a compelling enough reason to have a 7.62x39 again.