Short answer: buy a complete upper if you want it ready to bolt on. Build one from parts if you want to choose every piece. Either way, caliber and barrel length lead the decision.
What a complete upper has
The receiver, barrel, handguard, gas system, bolt carrier group and charging handle. You add it to your lower and a magazine.
Caliber and use
5.56 is the all-round choice. .300 BLK, 6.5 Grendel, 6mm ARC and .22 ARC each suit a job. See our build guide to compare.
Compatibility
Check your lower, magazine and buffer system before buying. The BCG compatibility guide helps with the bolt carrier.
What to look for
- Barrel: length, twist and chamber, such as 5.56 or .223 Wylde.
- Gas system: must match the barrel length and your handguard.
- Handguard: free-float handguards help accuracy and give mounting space.
- Bolt carrier group and charging handle: complete uppers include them, while stripped or barreled uppers do not.
Complete or build your own
A complete upper is the fastest way to a working rifle. A barreled upper lets you choose your own bolt carrier group and charging handle. A stripped upper gives you full control over every part.
Check the lower
Make sure the upper fits your lower receiver and that the buffer and spring match the gas system.
Keep building
Browse AR-15 parts, read the custom AR-15 build guide, or let our Palmetto, FL shop help with gunsmithing and custom AR builds.
Matching an Upper to Your Use
A home or range rifle does well with a 16 inch barrel and a mid-length gas system, which is smooth and reliable. A compact build for tight spaces uses a shorter barrel, while a precision or long range build uses a longer, heavier barrel and a free-float handguard. Decide how you will use the rifle first, then pick the barrel, caliber and gas system to match.
Quality Points
Look for a quality barrel steel with a proper finish, a staked gas key, and a bolt that is tested. These details decide how long the upper runs without problems. Browse our custom AR builds page if you want us to put one together for you.
Shop AR-15 parts at BMTC USA, a gun shop and gunsmith in Palmetto, FL.