STEP BY STEP AR-15 UPPER ASSEMBLY: How to build an AR 15 upper receiver

In this video

AR-15 Upper Assembly – stripped upper receiver on blue background for step-by-step tutorial
Detailed AR-15 Upper Assembly tutorial image from The Rogue Banshee’s complete build guide.

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Home » Watch & Learn » Disassembly & Reassembly » STEP BY STEP AR-15 UPPER ASSEMBLY: How to build an AR 15 upper receiver

AR-15 upper assembly doesn’t have to be complicated. Whether it’s your first build or just your first time doing it right, this step-by-step guide shows exactly how to assemble an AR-15 upper receiver from start to finish. Every tool, every part, every mistake to avoid—laid out clean and simple.

TL;DR – Full AR-15 Upper Assembly Checklist

  • Start with the forward assist and dust cover before barrel install

  • Grease matters: use white lithium on barrel extension and threads

  • Barrel nut torque: 30 ft-lbs ×3, final align under 80 ft-lbs

  • Align gas tube slot carefully or your BCG will bind

  • Handguard and carry handle go on last to finish the build

  • Tools Needed: punches, roll pin starters, torque wrench, armorer’s wrench, vise

What tools and parts do you need for building an AR-15 Upper Assembly?

How to assemble the AR-15 forward assist

Tip: Make sure the pawl engages the bolt carrier teeth. Test spring tension before installing the roll pin.

How to install the AR-15 forward assist

  • Slide the assist into the receiver

  • Hold with a 3/32″ punch

  • Start roll pin with starter

  • Drive flush with a 3/32″ punch

  • Test for smooth, springy movement

Insight: A properly seated forward assist should move freely but return firmly under spring tension.

How to install the AR-15 dust cover

  • Orient spring and pin correctly

  • Clip side of pin faces forward

  • Slide spring and door into place

  • Twist spring clockwise to tension

  • Push pin through while aligned

TIP: Use a pencil to pop the cover open. It should snap fully. If not, recheck spring twist.

How to assemble the AR-15 barrel nut assembly

  • Stack slip ring, spring, and snap ring onto barrel nut

  • Use snap ring pliers for the retaining ring

  • Align all three grooves so spring hole and snap ring slot match

Tip: Misaligned rings will block the gas tube and prevent proper torque alignment.

How to install the AR-15 barrel

  • Grease barrel extension and threads (white lithium)

  • Insert barrel into upper; align locating pin

  • Thread barrel nut by hand

  • Torque to 30 ft-lbs ×3 using armorer’s wrench

  • Back off and repeat for seating

SPEC: Final torque must not exceed 80 ft-lbs. Stop when gas tube slot lines up.

How to install the AR-15 gas tube and gas block

  • Align barrel nut so gas tube can pass through

  • Torque final setting to no more than 80 ft-lbs

  • Install gas tube, handguard cap, and FSB

  • Hammer in taper pins (right to left)

  • Align and pin gas tube

TECH: Gas tube should drop below the centerline. Taper pins must only go in from the right side.

How to install the AR-15 flash hider

  • Apply crush washer or peel washer

  • Thread flash hider on by hand

  • Torque until properly timed (ports up)

Manual Note: Only use 1/4 turn past hand-tight to time correctly.

How to install the AR-15 bolt carrier group

  • Insert charging handle first

  • Slide in BCG behind it

  • Make sure both lock into place

How to install the AR-15 upper onto the lower

  • Align pivot and takedown pins

  • Push pins through until seated

  • Function check upper/lower fit

How to install the AR-15 handguards

  • Compress delta ring

  • Insert front of handguards into cap

  • Seat rear under delta ring, release

How to install the AR-15 carry handle

  • Align with rear pic rail

  • Tighten thumb screws evenly

  • Confirm zeroing or co-witness height

Every time I build an upper, the one thing I still have to stop and double-check is the dust cover spring. That clockwise twist for tension trips me up more than anything else. I’ve learned to test the flip before I seat the pin — saves time and frustration every single time.Jason Schaller

FAQ – AR-15 Upper Receiver Assembly

What torque should you use on the barrel nut?
Start with 30 ft-lbs ×3, then increase gradually to align the gas tube slot — never exceed 80 ft-lbs.

Do you need to grease the barrel extension?
Yes. White lithium grease helps prevent galling and ensures smooth seating.

What if the gas tube doesn’t align?
Back off the barrel nut slightly, realign the retaining ring, then torque again.

Do you need a vise to build an upper?
Yes. Trying to torque without one risks damaging threads or alignment.

Should the forward assist be tight or loose?
It should move freely under spring tension without binding.

🔄 Need to field strip your AR-15?

Watch the full guide here: How to Field Strip an AR-15 or AR-10 – Step-by-Step Breakdown

Covers magazine removal, bolt carrier group extraction, buffer spring inspection, and safety checks. Quick and to the point—just how Joe likes it.

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Original Content by The Rogue Banshee / My Rogue Solutions LLC.
Credit: Jason Schaller
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About the Author: Jason Schaller is a former FFL holder and founder of Eagle Eye Shooters Supply in Helena, MT, where he provided professional gunsmithing services and guided customers on all aspects of firearms ownership. Today, he teaches DIY gunsmithing at The Rogue Banshee and serves as a Chief Instructor at Freedom Crew University. With over a decade of hands-on professional experience with firearms and nearly 30 years in IT, Jason also holds top cybersecurity certifications including CISSP, CISA, and CRISC. When he’s not geeking out, he’s helping others build self-reliance, critical thinking, and firearms proficiency through real-world content.

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