I had a 5.56 NATO version. Trigger was two stage and it was great. Ultimately the rifle failed to keep me interested like I thought it would. That is more my fault, as I set the expectations very high.
The SIG 556R had a lot confusion around it, mixed messages from SIG USA, can you shoot Russian steal ammo, yes or no. Back and forth it went. Something about a shim or sleeve or something in the receiver or magwell area, not sure.
There is no doubt that the design is solid. That can be said of the Robinson Arms XCR as well.