AR-15 Accuracy Fundamentals: Building a Sub-MOA Rifle
Modern AR-15s can absolutely shoot sub-MOA (minute of angle) groups, but achieving this requires understanding the components that matter and eliminating variables that don’t. Building an accurate rifle means making deliberate choices about barrel quality, ammunition, triggers, handguards, and setup rather than chasing the latest tactical gadget.
Barrel Quality and Material
The barrel is your foundation for accuracy. Match-grade stainless steel barrels from quality manufacturers like Krieger, Douglas, or Bartlein are proven performers. Barrel contour affects accuracy by controlling harmonics—heavier contours (government or match weight) stabilize barrel whip better than lighter profiles. A 1:8 or 1:9 twist rate accommodates most bullet weights effectively. For sub-MOA performance, start with button-rifled or hammer-forged barrels from reputable makers, which maintain tight tolerances and consistency.
Understanding Bore and Chamber
Bore concentricity—how perfectly centered the bore is within the barrel body—directly impacts accuracy. Quality manufacturers hold bore dimensions to extremely tight tolerances. Chamber dimensions matter equally: a properly dimensioned chamber ensures consistent bullet seating and firing. .223 Wylde chambers excel for accuracy because they combine tight tolerances with flexibility to shoot both .223 Remington and 5.56 NATO ammunition reliably.
Trigger Quality: Non-Negotiable
A quality trigger separates sub-MOA shooters from the rest. Mil-spec triggers have overtravel, creep, and inconsistent breaks—fine for defensive rifles but detrimental to accuracy. Match-grade triggers (2-2.5 lb break weight, clean break, minimal overtravel) from Geissele, Elftmann, or CMC Triggers reduce shooter-induced error significantly. A predictable trigger lets you focus on marksmanship rather than fighting mushy breaks.
Free-Float Handguards: Isolation is Key
A free-floated barrel—one that doesn’t touch the handguard or receiver beyond the barrel extension—provides consistency from shot to shot. As the barrel heats and cools, it harmonics differently if constrained. Free-float handguards isolate the barrel from external pressure, eliminating a major variable. This single upgrade transforms many factory rifles. Ensure gas tube doesn’t contact the handguard and that the barrel doesn’t touch the handguard anywhere along its length.
Bedding and Receiver Machining
Receiver flatness matters more than shooters realize. Mil-spec receivers from quality manufacturers maintain tolerances within .003″ of true, which is adequate for most shooting. For competition or long-range work, billet receivers or receivers with matched upper and lower tolerances reduce slop and improve repeatability. Some precision shooters lap upper/lower receivers to improve fit, though this is rarely necessary with quality manufacturing.
Ammunition Selection and Consistency
You cannot shoot sub-MOA consistently with variable ammunition. Match-grade ammunition like Federal Gold Medal Match, Hornady Match, or hand-loaded ammunition with consistent charges and bullets delivers the consistency required. Poor ammunition introduces variables—bullet runout, velocity inconsistency, weight variations—that no rifle setup can overcome. Invest in quality ammunition as much as quality components.
Optics and Mounting
Quality optics and solid mounting matter tremendously. Mid-range quality optics (Leupold, Nightforce, Vortex Optics) provide glass clarity and reticle integrity necessary for precision shooting. Mounting rings must be properly torqued (usually 25-30 in-lbs) to prevent slippage. A quality 1-piece mount provides better precision than split rings.
Gas System Tuning
Proper gas system tuning reduces felt recoil and improves follow-up shot accuracy. Over-gassing (common in factory rifles) creates excessive bolt carrier group velocity, leading to harder recoil and shot dispersion. Tuning the gas block to provide just enough gas for reliable cycling under all conditions improves accuracy noticeably. This might involve adjustable gas blocks and testing different buffer weights.
Muzzle Device Considerations
While suppressors significantly reduce noise, they can affect accuracy if not properly engineered. Direct-thread suppressors can shift point of impact if threads wear unevenly. Quick-detach systems occasionally introduce small point-of-impact shifts. For maximum precision, conduct a zero with your specific muzzle device installed. Brakes and flash hiders introduce muzzle signature variables, so minimizing these helps precision work.
Building Your Accurate Rifle
Sub-MOA performance requires a deliberate approach: start with a quality barrel, ensure free-floating, install a match-grade trigger, use consistent ammunition, mount quality optics, and eliminate tolerance stack-up where possible. These fundamentals consistently produce sub-MOA rifles. Avoid overbuilding with exotic upgrades—focus on the proven variables that demonstrably improve accuracy. With proper components and technique, modern AR-15s deliver accuracy that surpasses shooter capability in most cases.
