If you can't find an AR15 you like in your local store - you can just build one for around ~$1400
This guide gives builders some ideas on how to build an AR15 cheap and reliable.
A good build must start with a good barrel, and then we will work our way to finish the build to include the stock, bolt carrier group, optic and other optional accessories.
Let's find your parts now.
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Build A Cheap AR15 You Can Always Upgrade Later
Note: This guide only covers standard 16" 5.56mm barrel builds
Building a good AR15 rifle it's just like customizing cars, bikes, desktop computers, and many other manly things. Knowing exactly what parts to get is the key.
Budget AR 15 Build Ball Park Cost - Around $700 - 900 is considered "cheap" or "low cost" in the AR15 world for a fully functional rifle (Not including many useful accessories). Due to inflation, a good $1000 AR15 in the past is about ~$1200 in today's money (2023).
High-End AR15 Build Ball Park Costw - Generally costs around $1700 and $2000. Some have the same parts as a basic AR15 but are packaged with other bells and whistles to up the price tag. An experienced AR person can quickly spot the difference.
Build Your AR Like Lego - There are so many ways to make the rifle more unique than the others
Build Your Dream Rifle - Clone your dream rifle from movies, military histories, and video games including M16A4, HK 416, BRN 180 and many more.
AR15 Parts Priority
- Barrel - Don't cheap out on the barrel even for a budget build, but a $500 math grade precision barrel may not be necessary
- Trigger - Makes a huge difference in shooting
- BCG - This is the engine of the rifle
- Buffer Spring - For better BCG return force & service life
- Stock - Must have
- Pistol Grip - Must have
- Handguard - Mount accessories
- Muzzle Device - Reduces muzzle shift & sway
- Other accessories - Optional
7 Core AR15 Upper Receiver Parts
A basic upper receiver consists of the following items:
- Barrel
- Muzzle device
- Main receiver
- Gas block
- Gas tube
- BCG (Bolt Carrier Group)
- Charging handle
- Front & rear sights (Optional for some builds)
- Dust cover (Optional)
- Forward assist (Optional for some)
- Optic
Try this complete classic upper that include everything. Builder can change parts later
To Build From Scratch
To make it low cost and reliable, any standard A2 milspec stripped AR15 receiver works.
Whether you spend $350 for a receiver or a $90 receiver, the $90 receiver is a better choice so you can allocate the money to buy something more expensive such as a good trigger and handguard.
These are our top choices:
Barrel
The barrel is the most important part of the rifle, and buying a 1:9 or 1:7 twist rate barrel with the following specs, and you're good to go:
- Cold hammer forged - Exceptional strength, grain structure, accuracy & finish
- 1:9 twist rate - Works well for 45 - 70 gr 5.56mm or 223 bullets
- Mid length gas system - For a standard 16" build, the best is mid-length gas system
- Medium (Government Profile) - Heavier than pencil barrel with a balanced weight and durability
Check out these awesome barrels:
FN 16" CFH Barrel Mid Length 1:7
PSA 16" M4 Barrel Carbine Gas Length 1:7
Ballistic Advantage 16" 223 WYLDE (Multiple Options, click to see)
Gas Block & Tube
Must match the gas tube length to the barrel the gas system is designed for.
In this guide, we recommend getting a mid length gas system, so a mid length gas tube is required.
If you're going with a free float handguard configuration, a low profile gas block is required.
Bolt Carrier Group
Most AR15 BCG on the market today are full auto rated, coated, gas key staked, HPT & MPI tested (Doesn't mean it will go full auto)
The BCG experiences the most stress on the rifle during cycling, so getting a high quality bolt without getting too fancy will get the job done.
- Nitride coated - Easier to clean
- Nickel Boron - Shiny, butter smooth & easier to clean
- Titanium Nitride - A bit exotic product for a high end AR build
There are many choices, for a budget build, please check out these:
PSA BCG - The Lowest Price
Bravo Company Manufacturing M16 BCG - Gunfighter's Favorite Brand
Brownells Nitride M16 BCG - Best Value
Faxon Lighweight BCG - Lightweight BCG Action
Charging Handle
For a budget build, a standard mil-spec charging handle will do just fine. If there is money left over, we highly recommend:
Forward Assist
For a reliable AR15 build, get the receiver with the forward assist to help you seat the bolt just in case.
Handguard
Free Float Handguard - More Mounting Spots, Better Barrel Harmonics & Features Anti Rotational Receiver Tab
Removable front sight required
Two Piece - Much Cheaper Option, Requires Old School Delta Ring
The handguard in many ways defines the rifle, and it's a large visible part of the rifle that enables accessories mounting and the way it looks and feels.
Why Does A Good Handguard Matter?
- A place to grab the rifle
- Mount lights and lasers
- Sling and grip attachments
- Mount bipod
If you don't plan on further upgrading the rifle or adding accessories, this will be optional and it will save you a lot.
For A budget build, these are the best options:
BCM MCMR Free Float Rail - 9", 10", 13" & 15"
By now you should probably have some ideas on what you can financially and responsibly afford to get all the parts you need.
Another way is to just buy a cheap rifle like the Smith Wesson M&P 15, and add a light, a sight and a sling later.
Check out these good AR15 you can buy for $1000 here.
Lower Receiver Parts
A basic lower receiver consists of the following items:
- Main lower receiver (Serialized part that requires background check)
- Trigger (It's worth spending more on the trigger that you will not regret)
- Trigger guard
- Pistol grip
- Bolt catch
- Battery Assist Device (Optional)
- Magazine release
- Safety selector
- Retainer pins
- Stock
- Buffer tube
- Buffer spring and buffer (Try Geissele Braided Wire Spring to)
You can get most of them in a lower parts kit including a mil-spec trigger
PSA now offers Retro M4 and M16A2 lower receivers with markings (Partnered with Harrington & Richardson)
Trigger
A drop-in trigger is highly recommended to make a low-cost AR shoot like a high-end rifle. A good trigger is by far the number 1 performance increase shooters immediately notice when comparing with other similar ARs.
A great aftermarket trigger will provide a better trigger pull experience for tighter group shots at longer distances, and a better trigger reset for fast follow-up shots.
Grip
A good grip makes a huge difference in how the shooter feels around his/her wrist in terms of biomechanics when operating the AR15 platform, and it's inexpensive.
Get a PDW steep angle grip, the BCM MOD 3 grip is by far the best.
- Allows shooter's wrist to stay in a neutral position without adding strain to the firing hand
- Great for PDW build
- Adds just a little bit more speed and less finger strain while shooting fast
- Slightly faster weapon draw from the low ready position
- Just looks and feels better in the hands
If you have a large hand, there are customizable AR15 grips for large hands that come with multiple different size grip panels to fit your need.
Buffer Tube
There are commercial and mil-spec buffer tubes. They do the same thing and they fit on any lower receivers you may have
- Mil-spec tube goes with a mil-spec stock.
- Commercial tube goes with a commercial stock AND Mil spec
Learn more about their spec differences here
We recommend just buying the tube instead of a complete set so you can allocate some money for something else.
Buffer Spring
We highly recommend the Geissele Super 42 Braided Wire Spring for its improved spring cycling harmonics and service life. Most importantly it eliminates the annoying AR15 twang sound in the buffer tube when firing.
It's the same spring we recommend on other high-end rifles including SBR builds, and definitely add this to the cart.
Rifle Stock
A good rifle stock makes a big difference in how sturdy the rifle feels when shouldered, and it makes the rifle feel very rock solid without any wobble.
There are tons of options out there, and to make it simple get the following:
Magpul CTR stock - Very good start for less than $70 (without buffer tube kit)
These also have built-in sling attachment points.
Other Accessories
After the base rifle is built, it's up to you to get all the accessories including optics.
The most common accessories for a home defense AR15 are:
- Optic
- Grip
- Weapon light
- Sling & sling attachment
A good optic today costs around $200 and can go as high as $890 for a red dot sight.
LPVO are also popular optic setups people now days have, and you can check out more here
Tools Required
- Punch pins & small nylon hammer
- AR wrench & Torque wrench
- Workbench vise clamp
- Chamber gauge
- AR receiver block insert
If you don't want to invest in tools to just build one rifle, buying a complete rifle or receiver set will be a better cost saving option.
Wrap Up
Building a low-cost AR15 is fun and educational!
Through the process, it also teaches you the AR15 system and what parts actually move the needle in terms of performance.
To further upgrade your AR, these are important parts to consider:
- BCG
- Barrel
- Muzzle device
- Tougher and more modular handguards
- Fire selector
As the content creator of badassoptic.com, My background in the firearms industry and shooting sports gives me the experience to recommend tried and true products and keep away subpar ones.
