Obviously, not everyone who knows this stuff has a good blog, and not everyone who has a good blog knows his stuff. *I* think the ones I have listed are worth reading. They make sense to me, and to the people I know who have seen combat. Caveat: I have no combat experience and cannot provide recommendations or evaluations of the merits of the suggestions on these blogs as they relate to preparation for conflict, so I rely on the opinions of those who do. YMMV.
I will also say this- I can teach you the theoretical basis for perfect marksmanship in 30 seconds, but it will take years or even decades to develop the practical skill to bring theory to fruition. Put another way, there are some things you cannot learn from books, and I say that as a life-long bibliophile. For some subjects, experience is essential, and warfare is one of those.
BTW, the secret to perfect marksmanship? Ensure that perfectly adjusted sights are perfectly aligned with the target when the weapon fires. That's it. Being able to DO that, however, is a lifelong pursuit.