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[HERO IMAGE: AR-15 parts layout or assembled rifle]
How to Choose AR-15 Parts
Choosing AR-15 parts doesn’t have to be overwhelming. This guide breaks down each major component, explains what actually matters, and helps you build a reliable, compatible rifle based on how you plan to use it.
This guide is brand-agnostic and builder-focused. Use it alongside our build paths to avoid common mistakes.
How to Use This Guide
Start with intent
Range use, home defense, competition, or duty-style builds all prioritize different components.
Choose compatible parts
Receiver fit, gas system length, and barrel specs matter more than brand names.
Upgrade where it counts
Barrels, BCGs, and triggers have the biggest impact on performance and feel.
Lower Receivers: The Foundation
The lower receiver is the serialized core of your AR-15. Most forged lowers are similar in strength, but features and fit can vary.
- Forged vs billet: Forged is durable and cost-effective; billet focuses on aesthetics
- Mil-spec compatibility: Ensures parts fit without modification
- Ambidextrous features: Useful but not required for most builds
For first-time builders, a forged mil-spec lower is the safest and most versatile option.
Shop Lower Receivers[IMAGE: AR-15 lower receiver]
Upper Receivers: Compatibility Matters
Upper receivers house the barrel, BCG, and charging handle. Compatibility with your lower and handguard is more important than cosmetic features.
- Standard AR-15 upper receivers fit most builds
- Match handguard mounting systems carefully
- Forward assist and dust cover are optional but recommended
Barrels: Accuracy, Length & Gas System
The barrel has the biggest impact on accuracy and recoil. Choose it based on how you plan to shoot, not just what looks good.
- Common lengths: 10.3″–11.5″ (pistol), 16″ (most popular), 18″+ (precision)
- Gas systems: Carbine, mid-length, rifle — mid-length offers smoother recoil
- Twist rates: 1:7 or 1:8 cover most ammo types
For most builders, a 16″ mid-length barrel is the best balance of performance and reliability.
Shop Barrels[IMAGE: AR-15 barrel with gas system]
Bolt Carrier Groups (BCG): Reliability First
A quality BCG ensures proper cycling, extraction, and long-term reliability. This is not the place to cut corners.
- Materials: Carpenter 158 or 9310 steel bolts
- Coatings: Phosphate, nitride, or nickel boron
- Gas key: Properly staked is non-negotiable
Choose reliability over aesthetics — performance coatings are a bonus, not a requirement.
Shop BCGsHandguards: Fit, Length & Mounting
Handguards affect ergonomics, accessory mounting, and barrel clearance. Most modern builders prefer free-float designs.
- M-LOK vs KeyMod: M-LOK is the current standard
- Length: Longer handguards provide better control
- Clearance: Must match your gas system and barrel length
[IMAGE: AR-15 handguard with M-LOK]
Triggers: Feel & Control
Triggers dramatically affect how your rifle feels. Even modest upgrades can improve control and consistency.
- Single-stage vs two-stage depends on shooting style
- Lower pull weight ≠ better for every shooter
- Reliability matters more than ultra-light pulls
Muzzle Devices: Control vs Flash
Muzzle devices manage recoil and flash but should be chosen based on your shooting environment.
- Brakes: Reduce recoil but increase blast
- Flash hiders: Reduce muzzle flash
- Thread pitch: Must match your barrel
Customization: Cerakote & Laser Engraving
Custom finishes don’t change function, but they do change ownership experience. Cerakote adds durability and corrosion resistance, while laser engraving adds personal identity.
Learn About Cerakote & Laser EngravingNot Sure Where to Start?
If this is your first build, follow one of our proven build paths to avoid compatibility issues and get a complete parts list.
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