| Tier Level | Recommended Brand/Upper | Why to Choose |
|---|---|---|
| Entry (budget but vetted) | Palmetto State Armory Premium or CHF lines. Stick to their complete uppers with FN cold hammer-forged barrels when possible. | Solid QC for the money and great warranty support. Avoid mystery clearance batches and no-name barrels. |
| Mid-range | Aero Precision complete uppers. Choose pinned gas blocks where available and stick with their 4150 CMV or stainless options. | Good balance of price, machining quality, and parts availability. Plays nicely with most lowers without fitment drama. |
| Duty-grade | Bravo Company (BCM) complete uppers. Choose their BFH (hammer-forged) if you want maximum barrel life. | Proven reliability, conservative gas, and excellent customer service. Ideal for training-heavy schedules. |
| Top tier | Geissele Super Duty complete uppers. Available in 11.5", 12.5", 14.5", and 16" configurations with their proven reliability rail. | Premium triggers, tight tolerances, and excellent fit/finish. Built for hard use with strong factory support. |
Your first build should be dead simple: quality parts, zero custom headspace work, and a clear upgrade path.
First time building? Review the Common Beginner Mistakes guide before you start—it'll save you time and frustration.
The lower receiver is the regulated part. Order a stripped lower online from a reputable manufacturer and ship it to your local FFL for transfer, or buy one directly at the shop. Bring ID, complete the 4473, and keep the receipt with your serial number for records.
Avoid bargain-bin or polymer lowers (unless it's a reinforced KP-15). Stick with forged 7075-T6 from brands like Aero, BCM, Geissele, or PSA. Check that the takedown pins move smoothly before you leave the counter.
Under federal law, a rifle with a barrel under 16 inches or overall length under 26 inches is a Short-Barreled Rifle (SBR) and regulated under the NFA. You need an approved Form 1 or Form 4 before assembling or possessing an SBR with a stock. If you want to run a sub-16" barrel without NFA paperwork, configure it as a pistol (no stock) or register it.
Pistol braces are currently permitted on AR pistols under the latest federal guidance, but you must still follow state laws and avoid adding a stock unless you have SBR approval. Easiest compliance path for beginners: stick with a 16"+ complete upper unless you have paperwork in hand or are staying in pistol configuration.
Important: A stripped lower receiver can be built into either a pistol or rifle configuration—you decide when you assemble it. However, a firearm originally manufactured or sold as a rifle can only ever be a rifle or SBR, never a pistol. This is why starting with a stripped lower gives you maximum flexibility.
Tools needed: Armorer's wrench, punch set, torque wrench (in-lb and ft-lb), vise block, and a clean workspace. See our AR Tools Guide for the complete list and recommendations. Torque specs and threadlocker guidance are in the reference section below.
A solid lower parts kit gives you reliable springs, detents, and controls. Avoid no-name kits; pick PSA, Aero, BCM, SOLGW, or Forward Controls–sourced components. Reference the Lower Parts Quality Guide for vetted options.
Select the trigger that matches your mission (mil-spec for duty durability, or a known single-stage/2-stage upgrade like ALG ACT, Geissele SSA, or LaRue MBT). Add an ergonomic grip you like and a stock or brace that locks up tight. Torque the castle nut to spec and stake it; this prevents loosening over time.
Start with a carbine H2 buffer for most 16" 5.56 setups, then fine-tune only after live-fire. See the Gas System & Buffer Tuning guide if you need to adjust buffer weight or springs.
For a step-by-step visual walkthrough, check out Pew Pew Tactical's lower assembly guide—it has detailed photos for every step.
Starter lower picks that avoid no-name parts: a quality LPK, proven trigger, and a solid adjustable stock.
Known-good small parts without a trigger included, so you can pair it with your preferred FCG. CMMG kits have consistent dimensions and better QC than bargain-bin options.
A crisp two-stage with consistent pulls and excellent reset that rivals pricier options. Great for a first build that still wants precision and control.
Lightweight, anti-snag profile with a solid cheek weld and minimal rattle. A dependable choice for general-purpose builds.
Stick with a mil-spec diameter tube, end plate, castle nut, and carbine buffer/spring combo from a reputable brand. Avoid commercial-diameter tubes to keep stock fitment simple.
Start with an H2 for most 16" mid-length or carbine systems to tame gas without short-stroking. Adjust only after test fire and gas tuning.
Purchasing through these links may generate a commission at no extra cost to you. Verify compliance for any serialized parts and follow local/state laws.
Buying a factory-complete upper skips headspace checks, gas-port guesswork, and alignment issues. Pick the tier that matches your budget and intended use, then verify it includes a bolt carrier group (BCG) and charging handle or add those from the same brand.
Palmetto State Armory Premium or CHF lines. Stick to their complete uppers with FN cold hammer-forged barrels when possible.
Solid QC for the money and great warranty support. Avoid mystery clearance batches and no-name barrels.
Aero Precision complete uppers. Choose pinned gas blocks where available and stick with their 4150 CMV or stainless options.
Good balance of price, machining quality, and parts availability. Plays nicely with most lowers without fitment drama.
Bravo Company (BCM) complete uppers. Choose their BFH (hammer-forged) if you want maximum barrel life.
Proven reliability, conservative gas, and excellent customer service. Ideal for training-heavy schedules.
Geissele Super Duty complete uppers. Available in 11.5", 12.5", 14.5", and 16" configurations with their proven reliability rail.
Premium triggers, tight tolerances, and excellent fit/finish. Built for hard use with strong factory support.
Before first range trip, lube generously, perform a function check, and verify gas block screws are torqued and pinned/secured. Start with quality magazines (Magpul, Lancer, Okay/SureFeed) to rule out mag-related malfunctions.
Vetted factory uppers that keep headspace and gas within spec—pick by budget and mission.
PSA's Premium/CHF lines use FN-made barrels and solid QC for the price. Look for mid-length gas and pinned gas blocks when available.
Clean machining, consistent gas, and easy parts support. Choose 4150 CMV or stainless barrels and pinned gas blocks when possible.
Conservative gas ports, excellent staking, and robust QC make BCM a reliable choice for high round counts. Opt for BFH barrels for maximum life.
Geissele's Super Duty uppers feature their proven reliability rail, chrome-lined barrels, and impeccable fit/finish. Available in 11.5", 12.5", 14.5", and 16" configurations.
Purchasing through these links may generate a commission at no extra cost to you. Confirm barrel length and muzzle device compliance (pin-and-weld or NFA paperwork) before ordering.
Specific complete uppers we've selected for their value, quality, and availability on Optics Planet.
The standard-length Super Duty for general purpose use. Chrome-lined barrel with mid-length gas.
Compact 12.5" configuration for SBR or pistol builds. Same Super Duty quality in a shorter package.
The shortest Super Duty option for close quarters. Requires NFA paperwork or pistol configuration.
Lightweight pencil barrel with ATLAS handguard. Pin-and-weld ready for 16" overall with the right muzzle device.
Lightweight 16" upper from Daniel Defense with cold hammer forged barrel and M-LOK rail. Battle-proven reliability.
Match-grade .223 Wylde chamber with KeyMount muzzle brake. Radian's precision machining and ambidextrous heritage.
LWRCI's DI system brings their piston-driven reliability expertise to a lightweight direct impingement platform. Features cold hammer forged barrel and LWRCI's proven rail system.
Purchasing through these links may generate a commission at no extra cost to you. Confirm barrel length and muzzle device compliance before ordering.
Before loading any ammunition, verify your rifle functions correctly. Clear the weapon visually and physically—lock the bolt back and confirm the chamber is empty.
Warning: Never drop the hammer on your lower receiver without the upper installed. The hammer striking the bare receiver can crack the aluminum over time. Always complete your upper/lower assembly before testing trigger function.
If any step fails, diagnose before live fire. Common issues include improperly installed safety detent springs, trigger pin walk, or a misaligned bolt catch. Double-check your lower parts installation.
Clean threads with degreaser before applying. Blue Loctite is removable with heat; Rocksett requires soaking.
After assembly, run a 300–500 round shakedown with quality ammo and mags. Track malfunctions, then adjust buffer weight or springs only if needed—see the Gas System & Buffer Tuning guide for diagnostics.
When you're ready to add glass, check out the Optic Selection Matrix to find the right optic for your use case, then follow the Optic Mounting Basics guide for proper installation. Planning to run suppressed? Start with the Suppressor Compatibility Basics guide.
You are responsible for complying with all federal, state, and local laws, including NFA rules, pistol brace guidance, and transfer requirements. This guide is informational only and is not legal advice—consult an attorney or your FFL if you have questions about what is lawful in your jurisdiction.
Ready to continue? Here's the recommended next guide:
Avoid common AR-15 beginner mistakes: cheap parts quality issues, anodized red/blue parts, 5.56 short barrel problems, skeletonized components, Armaspec SCS failures, Olight safety hazards, and Amazon counterfeit optics.
Or explore a related topic:
AR-15 Tool Guide->Continue exploring with these related resources
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Complete AR-15 PDW and pistol build guide. Compare barrel lengths from 7" to 12.5", DDM4 PDW vs BCM Recce-11, .300 Blackout vs 5.56 for short barrels, pistol brace options, and current legal status.
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