300 Blackout vs 5.56: Which AR-15 Caliber Should You Choose?

5.56 is cheaper per round, flatter shooting at distance and the AR-15 default. 300 Blackout puts a heavier .30 caliber bullet in the same rifle with only a barrel change, works well in short barrels, and has subsonic loads that are quiet with a suppressor. Never let 300 BLK get into a 5.56 rifle.

At a Glance

	5.56 NATO	300 BLK
Bullet diameter	.22 caliber	.30 caliber
Common bullet weights (our listings)	55, 62, 75, 77 gr	110, 125, 150 gr supersonic; 190 to 220 gr subsonic
Best barrel length	Rifle and carbine length	Short barrels and AR pistols
Suppressor use	Supersonic	Subsonic loads available
Cost per round	Usually lower	Usually higher
Magazines	Standard AR-15	Standard AR-15 (mark them)
Shop	5.56 ammo	300 BLK ammo

300 Blackout vs 5.56 Ballistics

Factory figures for supersonic and subsonic 300 Blackout and a common 5.56 load.

Load key: FMJ = full metal jacket.

Load (Federal data)	Velocity (fps)	Energy (ft-lb)
Federal American Eagle (AE300BLK1) 300 Blackout 150 gr FMJ Boat-Tail	1900	1202
Federal American Eagle (AE300BLKSUP2) 300 Blackout 220 gr Open Tip Match	1000	488
Federal American Eagle (AE193) 5.56x45mm 55 gr FMJ Boat-Tail	3165	1223

Figures are as published by Federal Premium on each product page (checked October 30, 2026). Velocity from your own barrel will differ.

Same Rifle, Different Barrel

300 BLK was designed to use the standard AR-15 bolt, lower receiver and magazines, so switching usually means a new barrel or upper.

Safety Warning

A 300 BLK round can chamber in a 5.56 rifle, and firing it can destroy the rifle and injure you. Mark 300 BLK magazines and ammo cans clearly and never mix them.

Suppressed and Short Barrel Use

300 BLK's subsonic loads are quiet with a suppressor, and its supersonic loads are designed to work well from short barrels. 5.56 generally needs a longer barrel to perform as designed.

Range, Hunting and Cost

5.56 is the better choice for longer-range target shooting and cheap high-volume practice. 300 BLK with an expanding bullet is popular for hogs and deer at short range where legal.

Shop Both

5.56 ammo | 300 Blackout ammo | AR uppers | AR pistols. Compare current cost per round in our Ammo Price Index, see every cartridge in our ammo caliber chart.

Orders of $500 or more ship free; ammunition orders under $500 ship for $15.99. Ammunition is not returnable. Some states and cities restrict ammo purchases or shipments, so read our ammo and magazine laws by state before ordering. Tactical Surplus USA has been selling firearms, ammunition and gear since 2022.

FAQ

Can I use 5.56 magazines for 300 Blackout?

Generally yes. Mark them so they are never mixed up.

Can 300 Blackout fire in a 5.56 rifle?

It can chamber, and firing it is dangerous. Never load 300 BLK into a 5.56 rifle.

Which is better for home defense?

Both are used. Pick an expanding load designed for your barrel length and test it.

Is 300 Blackout more powerful than 5.56?

At the muzzle, Federal's 150 grain 300 Blackout lists 1,202 ft-lb and its 55 grain 5.56 lists 1,223 ft-lb. 300 Blackout fires a much heavier bullet at lower speed.

Is 300 Blackout good for hunting?

It is used for deer and hogs at short range with a hunting bullet. Check your state's rules.

Is subsonic 300 Blackout quiet?

With a suppressor, subsonic loads avoid the supersonic crack, but they are not silent.