{"id":19660,"date":"2026-07-15T22:05:36","date_gmt":"2026-07-15T22:05:36","guid":{"rendered":"https:\/\/www.wideners.com\/blog\/?p=19660"},"modified":"2026-07-15T22:05:36","modified_gmt":"2026-07-15T22:05:36","slug":"300-blk-vs-5-56-nato","status":"publish","type":"post","link":"https:\/\/www.wideners.com\/blog\/300-blk-vs-5-56-nato\/","title":{"rendered":"300 BLK VS 5.56 NATO"},"content":{"rendered":"

So, what to get? 300 BLK vs. 5.56 NATO is a hot debate. AR-15s rule the roost as America\u2019s rifle. The rifle\u2019s proliferation is due in part to decades of use by our armed forces, which have made generations of young men familiar with the platform. On top of that, the AR\u2019s standardization means parts are largely compatible across the board. A user can start with a serialized lower receiver and configure a rifle to serve whatever purpose they may need.\u00a0<\/span><\/p>\n

The recent reduction of the $200 tax stamp fee to $0 makes it more compelling for users to buy or convert their existing ARs into short-barreled rifles (SBRs). That puts users at a crossroads: what caliber to pick? In a short-barreled configuration, the two most likely options are 300 Blackout and 5.56 NATO. I\u2019ve shot thousands of rounds of both out of short-barreled ARs, and both have their place, with positives and negatives across the board. Below, we will pit the two against each other and see how the rounds stack up to your needs.<\/span><\/p>\n

300 BLK VS 5.56 NATO<\/strong><\/h2>\n

The 300 Blackout was standardized by<\/span> SAAMI<\/span><\/a> in 2011 and is based on the 5.56\/223 Remington case necked up to .308\u2033. However, there is some confusion about the cartridge\u2019s origin. J.D. Jones of SSK Industries originally necked the .221 Remington Fireball to .30 caliber. This round, the 300 Whisper, is nearly identical to the 300 Blackout, which was standardized by<\/span> AAC (Advanced Armament Corp)<\/span><\/a>. Why the two? J.D. Jones trademarked the name and required manufacturers to sign a licensing agreement to use 300 Whisper. This led to AAC\u2019s joint effort with Remington to develop a \u201cnew\u201d cartridge.<\/span><\/p>\n

However, it\u2019s safe to shoot 300 Whisper in 300 Blackout-chambered rifles (but not the other way around). <\/span>Hornady\u2019s eleventh edition reloading manual<\/span><\/a> even recommends using 300 Blackout data for 300 Whisper.<\/span><\/p>\n

The 300 Blackout was designed to deliver heavy .30-caliber bullets at subsonic speeds to overcome obstacles that stunted the 5.56. Bullet weights range from 110 grains to 225 grains, giving the 300 Blackout great flexibility in both subsonic and supersonic performance.<\/span><\/p>\n

European Persuasion<\/h4>\n

5.56 NATO<\/span><\/a> came out in the early 1960s. The 5.56 NATO became the primary rifle cartridge for nearly 60 nations. It was derived from the 223 Remington, which in turn was designed to replace the inadequate 222 Remington. The NATO-spec model differs from the commercial 223 Remington in a few key ways.\u00a0<\/span><\/p>\n

Notably, the chamber throat of a 5.56 is longer. Placing a 5.56 NATO round in a 223 Remington will cause chamber pressures to spike about 10,000 PSI above normal operating levels. Eventually, the 223 Wylde chamber was developed as a hybrid between the two. (Note: 223 Wylde is not a cartridge.) You can use 5.56 NATO for varmint control and service rifle matches,\u00a0 but it excels as a defensive cartridge.<\/span><\/p>\n

\n\n\n\n\n\n\n\n\n\n\n
Cartridge Specs<\/b><\/td>\n5.56 NATO<\/b><\/td>\n300 Blackout<\/b><\/td>\n<\/tr>\n
Parent Casing<\/span><\/td>\n223 Remington<\/span><\/td>\n5.56 NATO<\/span><\/td>\n<\/tr>\n
Bullet Diameter<\/span><\/td>\n.224\u2033<\/span><\/td>\n.308\u201c<\/span><\/td>\n<\/tr>\n
Neck Diameter<\/span><\/td>\n.253\u2033<\/span><\/td>\n.334\u2033<\/span><\/td>\n<\/tr>\n
Base Diameter<\/span><\/td>\n.378\u2033<\/span><\/td>\n.378\u2033<\/span><\/td>\n<\/tr>\n
Case Length<\/span><\/td>\n1.760\u2033<\/span><\/td>\n1.368\u2033<\/span><\/td>\n<\/tr>\n
Overall Length<\/span><\/td>\n2.250\u201c<\/span><\/td>\n2.260\u2033<\/span><\/td>\n<\/tr>\n
Grain Weight<\/span><\/td>\n55gr.-90gr.<\/span><\/td>\n110gr.-225gr.<\/span><\/td>\n<\/tr>\n
Max Pressure (SAMMI)<\/span><\/td>\n 60,000 PSI<\/span><\/td>\n55,000 PSI<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n

300 BLK vs. 5.56 NATO: Cartridge Specs & Overview\u00a0<\/strong><\/h2>\n

Ballistically speaking, this is where things get murky when comparing 300 BLK and 5.56 NATO. They are designed for radically different purposes. To keep this consistent, I\u2019ll be comparing each cartridge\u2019s use in an SBR\u2014something under 11.5\u201d.<\/span><\/p>\n

Dimensions for the 5.56 NATO:\u00a0<\/strong><\/h4>\n
\"a

Though they are almost identical, the 5.56\u00d745mm NATO cartridge is derived from the .223 Remington cartridge.<\/p><\/div>\n