Can't comment on the buffers; that's news to me. I've got half a dozen at the moment and you've got me curious where mine fall in weight; however, all of mine were sourced from HK between 2009-2011.
Regarding the springs, my first 416's all had one end painted red. Subsequent springs in later years had a red stripe down the center. And yeah, the overall length of springs even sourced at the same time varied about 1/4" in overall length.