556 NATO Reloading Data

Reliable 556 NATO reloading data requires understanding the distinct pressure differences between 5.56x45mm NATO and .223 Remington. Published data typically covers projectile weights from 55 grains up to 77 grains, detailing starting and maximum powder charges, muzzle velocities, chamber pressures up to military specification limits equivalent to roughly 62,350 PSI, cartridge overall length, and test barrel specifications. Because 5.56 NATO brass often features thicker walls and reduced internal case volume compared to commercial .223 brass, minor component variations, small rifle primer selection, and military crimp removal require careful attention.

556 NATO Reloading Data Overview

Bullet Style	Bullet Weight	Powder	Published Starting Load	Published Maximum Load	Published Velocity	Barrel Length / Firearm	Source
Hornady FMJ-BT	55 gr	Hodgdon CFE 223	25.0 gr	27.5 gr	2,900 to 3,150 fps	20″ / Test Barrel	Hodgdon / Hornady
Nosler Ballistic Tip	55 gr	Hodgdon Varget	25.5 gr	27.8 gr	2,880 to 3,120 fps	20″ / Modern Rifle	Hodgdon / Nosler
Barnes TSX	62 gr	Ramshot TAC	23.0 gr	25.5 gr	2,750 to 2,960 fps	20″ / Service Rifle	Ramshot / Barnes
Sierra HPBT MatchKing	77 gr	Hodgdon Varget	21.0 gr	23.5 gr	2,550 to 2,750 fps	20″ / Match Platform	Hodgdon / Sierra
Hornady BTHP	75 gr	Accurate 2230	22.0 gr	24.5 gr	2,600 to 2,800 fps	20″ / Test Barrel	Accurate / Hornady

Understanding The 556 NATO Reloading Data

Working up 556 NATO load data requires strict adherence to technical boundaries because military specifications differ from SAAMI commercial standards:

Pressure Differences: True 556 NATO loads operate at higher pressure thresholds than commercial .223 Remington, roughly equivalent to 62,350 PSI. Never use maximum 5.56 data in a firearm chambered strictly for .223 Remington unless verified.
Starting Load: The conservative minimum charge weight recommended by testing laboratories to ensure clean ignition and reliable gas cycling.
Military Brass Capacity: Surplus or military brass often has thicker web areas and reduced internal volume, which increases pressures and requires reduced starting charges.

556 NATO Powder Reloading Data

Selecting the correct propellant involves matching medium-burn-rate rifle powders that provide optimal port pressure for semi-automatic gas systems:

Powder	Bullet	Bullet Weight	Published Starting Load	Published Maximum Load	Published Velocity	Source
Hodgdon CFE 223	Hornady FMJ	55 gr	25.0 gr	27.5 gr	2,900 to 3,150 fps	Hodgdon
Hodgdon Varget	Nosler Ballistic Tip	55 gr	25.5 gr	27.8 gr	2,880 to 3,120 fps	Nosler
Ramshot TAC	Barnes TSX	62 gr	23.0 gr	25.5 gr	2,750 to 2,960 fps	Ramshot
Hodgdon Varget	Sierra MatchKing	77 gr	21.0 gr	23.5 gr	2,550 to 2,750 fps	Sierra
Accurate 2230	Hornady BTHP	75 gr	22.0 gr	24.0 gr	2,600 to 2,780 fps	Accurate

Component And Assembly Best Practices

Cartridge Overall Length: Standard specifications require an overall length typically set between 2.250 inches and 2.260 inches to ensure proper magazine feeding in AR-15 platforms.
Primer Pockets: Military brass frequently features crimped primer pockets. You must swage or ream the pocket before seating a new small rifle primer.
Crimp Requirements: A light taper crimp helps prevent bullet setback during rapid feeding in semi-automatic rifles.

Common 556 NATO Reloading Questions

Can I shoot 5.56 NATO reloads in a .223 Remington chamber?

Generally no, unless your barrel is marked .223 Wylde or 5.56 NATO, because the higher pressures and longer throat of 5.56 can cause dangerous overpressure in standard .223 chambers.

What are the best powders for 5.56 NATO?

Top-performing propellants include Hodgdon CFE 223, Varget, Ramshot TAC, and Accurate 2230.

Why does military brass require lower charges?

Military brass has thicker walls and less internal volume, which compresses powder charges and raises chamber pressure faster than commercial brass.