The AR-15 platform is one of the most customizable rifles on the market, which is exactly why so many first-time owners get stuck on the same question: should you buy a complete rifle off the shelf, or build one yourself from parts? Both paths get you to the same destination — a functioning, personalized rifle — but they differ a lot in cost, time, legal steps, and the learning curve involved. Here's how to think through the decision. Buying a Complete AR-15: The Straightforward Rout …