Build Sheet
AR-15 Build Sheet
The friendliest centerfire rifle build there is. Ten parts, an armorer's wrench, and an afternoon, and only one of those parts requires paperwork.
5.56 NATO · Carbine · Beginner · 2–3 hrs · Tools: Armorer's wrench, punch set, vise block
What this build is
The AR-15 is the build that made home assembly normal. Every dimension is standardized, barrels arrive headspaced from the factory, and the upper receiver is close to drop-in. There is no fitting, no timing, and no press work. The hardest thing you will do is stake a castle nut.
It is also the platform where piecing a rifle together genuinely competes on price, because the parts market is enormous and there is a blem or closeout version of almost everything. A careful builder shopping sales can land well under the price of a comparable complete rifle, with better parts in the places that matter.
The honest split is this: the lower is trivially easy and the upper is where the money and the decisions are. Many first-time builders assemble their own lower and buy a complete upper. That is not cheating, it is the sensible move if you do not want to buy a vise block and a torque wrench for one rifle.
The parts list and what it costs
Every part of the firearm itself, with a ballpark price for each. Optics, mounts and extra magazines go on top of this. The estimated total for this build is $520–$700, the sum of the parts below with a ±15% band around it, because prices move.
| Part | Ballpark | Notes |
|---|---|---|
| Stripped lower receiver · FFL | $60 | The serialized part |
| Lower parts kit (LPK) | $55 | Trigger, safety, springs, pins |
| Buffer tube kit + stock | $60 | Castle nut, buffer, spring, tube |
| Stripped upper receiver | $65 | Often sold assembled |
| Barrel - 16" 5.56 | $120 | 1:7 or 1:8 twist |
| Gas block + gas tube | $30 | Carbine or mid-length |
| Free-float handguard (M-LOK) | $75 | Raw / blem to save |
| Bolt carrier group (BCG) | $95 | HPT/MPI tested |
| Charging handle | $30 | |
| Muzzle device | $20 | A2 flash hider or brake |
These are ballparks, not quotes. Prices move weekly and we do not invent them. The deal board links straight to the retailer's own product page so you see the live price before you buy.
The part that needs an FFL
The stripped lower receiver is the firearm. It is the piece with the serial number, it ships to a licensed dealer, and you do the background check there. Every other part on this list (the upper, the barrel, the bolt carrier group, the handguard, the trigger, the stock) ships straight to your door with no paperwork at all. This surprises people, and it is the reason the AR parts market looks the way it does. Some states restrict specific configurations after assembly, particularly around stocks and magazines, so check your own law before you pick a stock.
Where to save
These are the parts where the budget version and the premium version are the same material with a different roll mark:
- Handguard. A raw or blem M-LOK handguard is the same extrusion as the expensive one. This is the biggest easy saving on the rifle.
- Stripped upper and lower receivers. Forged 7075 is forged 7075. Blems here are close to free money.
- Muzzle device. A standard A2 flash hider works and costs almost nothing. Upgrade later if you decide you care.
- Stock and grip. Purely ergonomic, so buy what feels right, not what costs the most.
- Charging handle. Fine to buy budget unless you are running a suppressor.
If you do not know what "blem" means on a listing, we wrote a guide on exactly that, and it is where most of the savings on this sheet come from.
Where not to save
And these are the ones where cheap costs you twice:
- Barrel. This is the accuracy and the safety of the rifle. Buy from a maker who publishes their steel and their testing.
- Bolt carrier group. Look for HPT/MPI testing: high-pressure tested and magnetic-particle inspected. The bolt is the part that fails, and a cheap one fails sooner.
- Gas block and gas tube. Cheap here means a rifle that short-strokes or will not lock back. Buy steel, and buy it once.
- Lower parts kit trigger. Springs and pins are commodity, but a gritty trigger will make you dislike the rifle.
Common mistakes
- Not staking the castle nut and the gas key. Both back out under recoil. Staking takes two minutes and prevents the two most common AR failures.
- Mismatched gas length: a 16" barrel is normally carbine or mid-length gas, and the gas tube must match the barrel's gas port location, not the barrel length.
- Launching detent springs: tape off the receiver around every pin and work over a towel or a shallow box.
- Over-torquing the barrel nut, or under-torquing it and having the handguard shift.
- Buying a 1:12 twist barrel. Get 1:7 or 1:8 unless you have a specific reason; 1:7 stabilizes everything.
- Assuming a factory-headspaced barrel means you are done. Headspace is a property of the barrel and the bolt together. If your BCG did not ship with your barrel, check it with go/no-go gauges before firing.
Before you load it
Do all of this with the firearm confirmed unloaded and pointed somewhere safe, before it ever sees live ammunition. It takes a couple of minutes and catches almost every assembly error:
- Function check. The hammer or striker holds when cocked, the trigger releases it, and the trigger resets.
- Safety check. With the safety engaged, the trigger does not release the hammer or striker. Check every safety the design has.
- Hand-cycle dummy rounds or snap caps. Watch them feed, chamber, extract and eject. Do it slowly and watch, not fast.
- Headspace. If your barrel and bolt did not ship together as a matched pair, check it with go/no-go gauges for your exact chamber before firing.
- First live rounds one at a time. Load a single round, fire, and inspect the case, then do it again, then load a full magazine.
If anything on this list does not behave the way it should, stop and take it to a gunsmith. That is a cheap afternoon compared to the alternative.
FAQ
Which AR-15 part needs a background check?
Only the stripped lower receiver. It is the serialized firearm and ships to an FFL. The barrel, bolt carrier group, upper receiver, handguard, trigger, and stock all ship directly to your door.
How much does it cost to build an AR-15?
Piecing one together from the parts on this sheet lands in the ballpark shown above at typical prices. Shopping blems and sales pushes it lower; premium barrels and triggers push it higher.
Is building an AR-15 cheaper than buying one?
It can be, unlike most platforms, because the parts market is so large. The bigger advantage is control: you choose the barrel and bolt carrier group instead of accepting whatever the factory installed.
Do I need special tools?
An armorer's wrench, a vise block, and a punch set. Add go/no-go headspace gauges if your barrel and bolt came from different vendors. If you buy a complete upper instead of assembling one, you can skip the wrench and vise block.
What twist rate should I buy?
1:7 or 1:8, since a 1:7 twist stabilizes heavier bullets and handles light ones fine, which makes it the safe default.
Price this build out
The deal board tracks parts for this build across the retailers builders actually use. Every listing links straight to the shop's own page for the live price.
Browse the gear →Affiliate disclosure: Cold Bore Index earns a commission when you buy through links on this site, at no extra cost to you. We link to real products at retailers you already use; prices and availability are shown live on their pages. We're not a dealer and hold no inventory. Nothing here is legal advice. Firearm laws vary by state and by city, and checking yours is on you.