Whether you're a first-time buyer, a seasoned builder, or just trying to keep up with the conversation at your local gun store, the AR-15 world can feel like it has its own language. BCG, FSB, MLOK, NiB, SBR — the abbreviations fly fast and furious. This guide breaks down the most common AR-15 acronyms so you can shop smarter, build better, and talk guns with confidence. First Things First: What Does "AR" Actually Stand For? One of the most common misconceptions in the firearms world is t …