Podcast 151 All About the 556 Round

By on January 20, 2016

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Today: Lots of information about the 5.56mm round and what it can do for you… and what it can’t do. Lots of myths out there but less facts. Here are some facts to help you determine what ammo you should use.


Podcast Outline:

Difference Between the 556 NATO and .223 Remington

  • 556 Case Mouth Conducer 55,000 PSI; but SAAMI says it’s closer to 60,000 PSI
  • .223 Copper Units or Measure (CUM) or called Mid Case Transducer, SAAMI says the max 55,000 PSI
  • SAAMI Spec vs NATO Spec Chamber
    • Chamber the same except the throat or lead
      • .223 is 0.085”
      • 56 is 0.162”
    • Cartridge Difference
    • Interchangeability (you can shoot .223 and 5.56 in a 5.56 NATO chamber, but not the other way around. Buy a 5.56 chambered gun)

Ammo I’ve Used

  • 556 NATO 62gr Green Tips (M855)
  • 556 NATO 55gr FMJ (M193)

Military Moving

  • M855A1
  • Marines stuck on M855
  • But using MK318 Mod 2 in combat
  • Rumors of 75 or 77gr long range bullets
  • Change is coming

For Home Defense

  • Trusted 55gr FMJ
  • Ballistic Performance
  • Everything else you give up performance in tissue to gain other things
  • Ammo companies and what they will give us


  • Do you need barrier penetration?
  • Length of Barrel
    • Creates different velocities
    • Different Velocities mean different yaw and shatter points
    • Shatter is what gets you desired effect
    • Has to being going fast enough
    • About
      • 2600 FPS or above to get shatter
      • 16” 2800 FPS at muzzle
      • 20” 3000 FPS at muzzle
      • From Ballistics by the inch
        • 18” 2983
        • 16” 2943
        • 14” 2878
        • 12” 2616
        • 10” 2380
      • Anything with a shorter barrel needs a different kind of ammo
      • Consider Hornady TAP
      • With short barrels and 55 gr bullets not much more then a 9mm
    • Consider the longest shot you may take
    • Wall Penetration
    • If you go extra heavy barrel twist matter


Thanks for listening, don’t forget to check out the Shooter’s Club.

Stay Safe,



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