Against my better judgment, I'm going to begin my 1st AR build. Right now, I have a completely stripped lower that I want to build up. If I understand correctly (and please correct me if I am wrong), a build-up of the lower is completely standard until you get to the extension tube / stock portion. Here's where I get confused. I think I understand the mil-spec vs commercial aspect (just make sure your stock has the same size threads as the extension tube). I opted for the mil-spec size, since it seemed to be more prevalent. But I'm thoroughly confused on a spring / buffer weight / stock. I see mention of "carbine" vs "rifle", and I don't understand. For example, on Bravo Company's website, they have 4 carbine buffers : standard, H, H2, H3, but only one rifle buffer. What's the deal here? I am not going to use an A2 stock, but am currently leaning towards a VLTOR. Even then, are there "carbine" and "rifle" stocks? Reading between the lines, I'm assuming I have to decide on what upper to build / buy, and that will determine what spring and weight to use. Is this correct? In my reading, it seems like "most" people recommend a non-carbine size (what is what exactly), but I don't know if this is from experience, or more like a glock vs. xd thing. Any help would be appreciated. Cheers!