9 Best AR15 Complete Upper Receivers [With Rock Solid Handguard System]

scalarworks aimpoint micro on mk18

The AR15 upper receiver has almost an unlimited ways to configure. 

In this guide, let's check out the best AR15 complete upper receivers chambered in 5.56/223 to buy.

Since there are almost hundreds of good ones to get, here at BadAssOptic we are narrowing the choice down to just 9 of the most popular ones with rock solid handguard systems, barrel lengths and gas systems and more.

Let's check them out...

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9 Best AR15 Complete Upper Receivers [All Types]

Note: Not all complete uppers include BCGs.

If you want to check out complete rifles, please browse this guide here

Daniel Defense DDM4V11 - Best Overall

DDm4v11 upper

Best selling point - The DDM4V11 mil-spec grade upper is designed for a variety of uses including shooting sports, tactical training, and home defense. Its long 15" KeyMod rail system gives the shooter the option to have the support hand extended out closer to the muzzle allowing them to drive the rifle more precisely and prevents over travel when transitioning between targets.

Reliable Mid Length Gas System - Unlike traditional carbine length gas system, the mid length gas systems lengthens the rifle's service life by reducing parts wear and also reduces recoil felt by the shooter

Pre-Installed Muzzle Climb Mitigator - It redirects the exiting gas through calibrated ports to counter recoil and muzzle climb, which gives competitor shooting shorter split times & more precise follow-up shot (If also combined with a good trigger & buffer system)

Daniel Defense MK18 - Best CQB SBR Upper

Why this is the best for an SBR - The DDMK18 rifle is the gold standard for a short barrel 10.3" AR15 with carbine length gas system for CQB style applications.

The DD RIS II free float rail system features the ultra-durable Bolt-Up system & full 9.55" length Picatinny mounting space for mounting any accessories, and it also features lower mounting points for an M203 grenade launcher(unlikely for civilians to easily obtain).

Rigorously Tested By USSOCOM - Fielded by the US Special Operation Command for the SOPMOD II program and meets the US Department of Defense Mil-Spec combat grade requirements

Non- Clone Upper - Unlike other AR15 builds that assemble various parts to look the part what the military has, this is the real deal MK18 upper great for SBR build or MK18 pistol build

Super Durable Barrel Nut System - The RIS II handguard locks onto the receiver using the Daniel Defense's patented anti rotational Bolt-Up system with Grade 8 fasteners that can withstand rough handling, drops and kicks

BCM MK2 w/MCMR 15 - Best Barrel Nut Mounting System

bcm mk2 bfh mid length upper

Why buy the BCM MK2 - The BCM MK2 features the lightweight MCMR rail system that mounts the handguard tight on the receiver with anti rotational tab to prevent shift due to heat, vibration and rough handling.

It's one of the best upper receiver set for a low budget AR build or a high end build

M4 Feed Ramp - M4 feed ramps built-in on the barrel aids feeding rounds (specifically more pointed bullets vs. rounded bullets) into the chamber from a magazine more easily.

MLOK Mounting Slots - Proven to be the stronger mounting system over KeyMod, the MCMR 15" rail features the full length MLOK mounting slot for any accessories

aero precision m4e1 upper

Why we picked this one - Aero Precision is the go to for custom build ARs, their M4E1 complete lower is as popular as the upper assembly. Through superior engineering, they have condensed the parts needed to mount a free-floated handguard to a mere 8 screws.

In addition, it is it a stronger system and lighter for more efficient cooling.

Aero Gen 2 Handguard - It features include the addition of quick disconnect sling sockets, enhanced milling design for grip and visual appeal and a new profile for the picatinny top rail.

  • Handguard mounting platform is forged into the receiver
  • Works with Aero Precision handguards but also fits most BAR-system handguards
  • Compatible with low profile gas blocks

Geissele URGI Upper - Best Durability

geissele urgi upper 14.5

What's special about this - This is the URG-I (Upper Receiver Group Improved) made for the USASOC (US Army Special Operation Command). This upper's biggest selling point is the Super Modular Rail MK 16 free float handguard (BCM MCMR rail on steroid) with superior rigidity, modularity & includes the Anti-rotation tabs that ensures the rail will not rotate, even under the most extreme conditions of use.

M855A1 (AB57) Ammo Capable - The cold hammer forged barrel is made to withstand the heat and wear of the M855A1 ammo type, which is known to be fired at a much higher pressure than the standard M855 ammo for increased penetration of armor and hard targets.

The powder burns faster and creates more pressure, and has the effect of reducing flash. The round yaws like the M855, but its yaw is more consistent and predictable for stable bullet in flight performance.

Enhanced Mid Length Gas System - The enlarged gas port in addition to the mid length gas system design enables the rifle to experiences less recoil and parts wear. In addition, it helps the rifle to push through malfunction by over gassing the system

Pinned Gas Block For Increased Durability - Pinned gas black is found on most high end ARs that are built for series use to ensure it doesn't shift or fall off under any circumstances.

Knight's Armament URX SR15 - Best Old School

Knight's Armament URX SR15 upper complete

Why this is still so popular - Besides the external appearance that feels just like any other AR15 uppers, the SR15 upper features a unique BCG system with rounded bolt lugs to increase the shear strength & unlocks easier after a round is fired.

When all that is combined... you get a durable weapon system with softer recoil.

But there is more...

Improved Dual Spring Ejector - The dual spring system increases the clamp force on the shell casing to ensure reliable extraction after each shot

Slick Looking & Rock Solid URX Rail System - Only a few picatinny rail sections are added to the most popular mounting locations on the handguard to reduce weight & it features QD mounting slots for sling attachment (Currently the URX 4 MLOK rail system is more popular)

Radian Weapon System Model 1 - Best Low Recoil Mid Length Upper

radian weapon system mod 1 upper

What people love this - This 14.5" barrel length with a mid-length gas system is by far the best low recoil upper compared to others on the market including the Geissele URGI. On top of that, the aesthetics of the billet 7075 T6 upper is a more badass looking than other boring A2 style receivers, and there are more...

Includes Radian Raptor SD Charging Handle - The Raptor charging handle is the best on the market for ambi use with large latches for better gripping, and the SD model is built to support suppressor use to eliminate gas blow back

Enhanced Barrel Nut & Handguard Mount - Radian's proprietary handguard mount

Preinstalled SilencerCO ASR Flash Hider - Ready for compatible suppressor

Match Grade 416R 223 Wylde Barrel - Increased accuracy with match grade barrel featuring the 223 Wylde chamber

BRN 180 Gen 2 - Best Side Charging Receiver

brn 180 upper receiver

What's unique about this one - The BRN 180 Gen 2 upper is significantly different than a traditional AR15 upper in the way it operates. It's inspired by the Armalite® AR-180 of the 1960s with side charging handle and incorporates many of the AR-18/AR-180 improvements - including its robust and reliable gas piston operating system.

223 Wylde Chamber - The hybrid optimized barrel chamber works for 223 and 5.56. While it being similar to a 5.56 chamber, the 223 Wylde provides a much tighter freebore size to shoot .223 ammo with relatively increased accuracy

Features Adjustable Gas System - Adjust the gas system for different ammunition use and suppressor, to ensure smooth and consistent function.

New Handguard Locking System - It ensures the handguard retains alignment and rigidity with the upper receiver.  Also, with this new takedown mechanism, the handguard can be removed to access the gas system without removing the internal components.  

pws 107 mod 2

Why this is the best for a piston system - The Primary Weapon System MK107 MOD 2 features the most reliable long stroke piston system for a 7" short barrel AR.

223 Wylde Chamber - The hybrid optimized barrel chamber works for 223 and 5.56.

3 setting Adjustable Gas Regulator - It allows the user to adjust the gas settings for suppressor use

Preinstalled PWS CQB 556 Muzzle - Designed to redirect sound forward for close-quarters combat to mitigate sound and blast while improving overall weapon control

Upper Receiver Buyer's Guide

ar15 receivers taken apart

You can purchase an complete upper receiver without 4473 background check (Current LAW 2021) because it's not a serialized part to be considered as a firearm. 

You can also buy a stripped upper receiver and build it from scratch with parts you want.

There are 4 types of AR-15 upper receivers

  • A1 (1960s): It enables accurate firing at up to around 450 yards and provides a 1:12 twist rate. Its flip rear sight is adjustable for windage, and the rear sight has both short- and long-range apertures. It has a light-profile barrel, a fixed-carry handle and forward assist.
  • A2 (1980s): Heavier barrel than the A1 model with a fixed-carry handle and forward assist to clear jam.
  • A3: The A3 kept all the great upgrades from A1 and A2, now it features detachable carrying handle which enables optic mounts. 
  • A4 (Mostly what you see on the market today): Mostly the same as A3, the A4 has M4-style feed ramps that works with existing M4 barrel.

Core Components

The AR15 upper receiver features a couple core components:

  • Main receiver
  • Barrel
  • Barrel Nut
  • Handguard
  • Forward Assist & Associated Retention Pins
  • Ejection Port Dust Cover
  • Charging Handle
  • Gas Block & Associated retention pins
  • Gas Tube Or Piston System
  • Bolt Carrier Group
  • Muzzle Device
  • Sights

Importance Of Getting A Good Bolt Carrier Group

AR15 bolt BCG

The bolt carrier group is the main action component of the AR15 rifle that's responsible for:

  • Loading a new round into the chamber
  • Fires that round
  • Extracts and ejects the spent casing
  • Cocks the hammer

NOTE: Some complete upper receiver package includes a BCG and some don't.

aero precision bcg nickel boron
ar15 bolt parts

It's the main engine of the rifle, and the process repeats and it experiences tons of stress over time. So a good bolt carrier group has the following military specs:

  • Chrome lined interior bolt carrier key and bolt carrier
  • Coated with a matte black mil-spec finish
  • Magnetic Particle Inspected (MPI)
  • High Pressure Tested (HPT)
  • Bolt carrier machined 8620 steel
  • Torqued and staked gas key screws
  • Heat treated and shot peened
  • Carpenter 158 steel bolt

Mil-spec BCG doesn't mean the BCG is the greatest or the worst. It's simply means the part is made to the military standard.

Gas System

ar15 gas block

The AR15 has two gas systems:

  • Direct Impingement (DI)
  • Piston Driven

Picking the right gas system directly impact how the rifle recoils and how it performs when using a suppressor.

The Stoner DI gas tube system is the most common, which involves redirecting the hot gas leaving the barrel back into the gun to recycle the bolt carrier group via the gas tube.

While the direct impingement system can be very reliable, there is no doubt that a lot of fouling can build up on the bolt carrier group.

There are 4 major DI gas system lengths:

  • Pistol 4"
  • Carbine 7"
  • Mid Length 9" - Most reliable & Softer recoil
  • Rifle Length 12"

The Piston Driven design uses the propellant gas to operate a rod that acts as an intermediary to exert force on the bolt carrier group to cycle the weapon.

All excess gas is bled out of the gun well forward of the receiver. This helps keep the guns extremely clean. Ultimately it's just like how an AK47 operates.

Barrel Quality & Performance

Most complete AR15 upper receiver ships with a barrel that is very high quality. The barrel affects accuracy, reliability, and handling of the rifle more than any other component on the upper.

Most AR15 barrels on the market today are cold hammered forged and magnetic particle tested for increased service life, accuracy and durability.

When selecting a barrel, we must balance accuracy, weight, handling, parts longevity, and recoil characteristics. The choices we have to make to affect these traits include:

  • Length
  • Profile
  • Material & lining
  • Barrel profile
  • Rifling method & twist
  • Chamber dimensions
  • Gas system

Barrel Materials

  • 4150 Steel - Used for Mil Spec barrels & Recommend for full auto rapid firing
  • 4140 Steel - Uses 10% less carbon than 4150 
  • Chrome Molybdenum Vanadium (CMV) - same as 4140 (Most common)
  • Stainless Steel - Shorter lifespan

Barrel Lining

There are 2 main types:

  • Chrome Lined - It makes the barrel last long and it's the most common in modern AR15 barrels (Most common)
  • Ferritic Nitrocarburizing (FNC) - It treats the rifling for better accuracy instead of using coating 

Depend on the legnth of the barrel, generally people will find barrels with these three twist rates:

  • 1/8
  • 1/9
  • 1/7

These twist rates are optimized for specific bullet weights, which is illustrated in the image below:

AR15 twist rate barrel chart

Barrel Nut & Handguard Locking System


AR15 designs have evolved over time, and they have been very innovative, strong and better. One thing particular is how the handguard is attached to the receiver compared to the old school delta ring assembly.

A good barrel nut system allows the handguard to be securely mounted on the receiver with anti rotational mechanism to prevent the handguard rail from shifting due to recoil vibration, rough handling or heat.

geissele rail anti rotational tabs


lmt one piece upper receiver

Features LMT MLC Upper, One-Piece Upper Construction

Another type of upper receiver that is very popular is the one-piece monolithic upper receiver where the barrel is held in place with a proprietary locking system that utilizes locking bolts accessible from the right side of the receiver.

Handguard Selection

geissele barrel nut system and installation kit

Picking a good handguard makes the AR stand out from the rest. It's the most obvious part of the rifle that gives the rifle its look and the capability to mount accessories.

In addition, modern AR handguards have improved mounting system on the existing A2 style receiver for providing rock solid handguard installation compared to the delta ring style mount.


The most popular handguard today is the free float system because no part of the handguard makes contact with the barrel, So the force exerted onto the handguard isn't transfered onto the barrel which helps increase accuracy and preserves barrel harmonics.

As far as mounting capabilities go, there are tons of options available, and the 3 most popular ones are:

MLOK mounting slot flexibility
  • M1913
  • MLOK
  • KeyMod

The two most modular options are MLOK and KeyMod, which give the AR15 a very clean, lightweight and streamlined handguard system that allows the user to mount any accessories as needed without having unwanted weight.

Forward Assist - Yes or No?

forward assist 15 part

The forward assist is an recommend component to have on the AR15 upper receiver to help seat the bolt fully for added reliability redundancy.

Some AR15s have removed the forward assist feature to make the rifle lighter and the cost slightly cheaper, but it's worth spending the extra money to have the forward assist to help seat the bolt if the bolt head gets stuck loading a round into the chamber.

Enhanced Charging Handle

raptor atx charging handle demo

A complete upper receiver generally ships with a standard-sized charging handle, and the user can swap out the charging handle at any time.

We recommend a charging handle with a over sized latch with an enlarged surface area for a better grip for shooters wearing gloves and better handling with one hand.

Check out: 3 Best AR15 Charging Handles

Another reason to upgrade the charging handle is to prevent gas blowback while using a suppressed rifle. People generally buy the Precision Flex M84 Gas Buster charging handle for that specific purpose.

Muzzle Device

mk18 muzzle brake at night

Great for fun, but not great for NV users or to reduce flash signature at night

be meyer 556 flash hider

Features BE MEYER 556 Flash Hider, Recommended for superior flash suppression

Most complete upper receivers come with standard birdcage A2 style flash hiders for reducing cost, and they can be swapped out with other types of muzzle devices (More expensive) designed to do the following:

  • Compensator - Reduces muzzle movement & dulls perceived recoil
  • Flash hider & compensator hybrid - Reduces recoil & hides as much flash as possible
  • Muzzle brake - Acts like a compensator, but reduces muzzle rise and recoil impulses significantly
  • Pinned & Welded (Not removable)- To fulfill the legal 16" barrel requirement when using a 14.5" barrel

All AR15 barrels have standard 1/2"X28 thread per pitch, and most AR15 muzzle devices will fit.

Flip Up Sights

magpul mbus pro steel flip up iron sights

Most complete upper receivers on the marketplace today come with Magpul front & rear flip-up sights. Some may not come with any, but it's okay.

Flip-up back up sights are removable, and they serve as back up co-witness iron sights in the event of optic failure.

As optic reliability and battery life have dramatically improved in recent years, most people confide in their optics to the point iron sights are never really used at all except for using them as a reference aiming point to zero red dot optics & lasers.

offset magpul iron sights on ar15

However, offset flip up sights can be advantageous for fast sights transition especially on rifles with magnified optics mounted. For offset aiming, people can use micro red dot sights on offset mounts.

T-Marked vs Non T-Marked

t marked top ar15 upper receiver

The numbers etched on the upper receiver between every other rail slot rail slot helps the user recall the last position the optic is mounted.

T marks doesn't affect the performance of the rifle at all.

Common FAQ

7075 T6 VS 6061 T6 Aluminum Receiver Comparison

The main upper receiver, charging handle and the handguard are generally made with 7075 T6 or 6061 T6 aluminum. When it comes to durability, they both work very well.

In fact, 6061 was the original selected aluminum type for making M16s up until 1968 when the military wanted 7075 for added corrosion protection.

6061 and 7075 Aluminum have different properties that make them attractive to manufacturers.

Aluminum Type6061 T67075 T6
Ultimate Tensile Strength45000 PSI83000 PSI
Tensile Yield Strength40000 PSI73000 PSI
Shear Strength30000 PSI48000 PSI
Fatigue Strength14000 PSI23000 PSI

Which To Use? The Difference Between M16 and AR15 BCG

One of the common questions people have is: Can you use an M16 bolt carrier in an AR-15?

The answer is yes, but only the M16 bolt has full auto capability (Only works with full auto sear) and it's the most common BCG on the market

What Are The Common Upper Receiver Parts That Tend To Wear Out?

Under normal use, the AR15 rifle will last over 20,000 - 30,000 rounds. The upper receiver has parts that are most likely to wear out and require replacement than the lower receiver parts.

  • Barrel - Wears out as more rounds are fired
  • Gas Block - It can get lose over time
  • Bolt - Bolt head & firing pin will experience accelerated wear and tear. In addition, splitting along the cam pin holes or the locking lugs break after excessive use
  • Extractor - It can be cracked, chipped, or even break as round counts increase
  • Handguard mount - Not necessarily break, but a weak barrel nut system will start to rotate and lose tightness due to vibration and heat

What Does Anti Rotational Handguard Tab Do?

Anti rotational tab works in conjunction with a rock solid barrel nut system. It's main purpose is to hold the handguard to the front of the upper receiver and prevent it from rotating due to rough handling, recoil vibration or heat over time.

Typical AR15 handguard rail systems don't lock onto the upper receiver, which can cause the handguard to mis align or shift.

So having a handguard system that features anti rotational tab is a feature all AR15 owners should have.

Is Having A Ejection Port Dust Cover Neccessary?

Ejection port cover protects the weapon system especially the bolt area from mud, sand, dirt and other unwanted things that can cause malfunctions.