Variations Between Common 5.56 and .223 Remington 55 Grain Loads

As I am sure many would attest, being “Mil Spec” does not necessarily mean that something will be the exact same between different manufacturers. Manufacturing methodologies, tolerance stack-ups, etc all contribute to variations of the same product. A prime example of this is various military weapons from World War 2 and today.

In a remarkable comparison, shooter Jonathan Ocab cataloged differences between various common 55 grain .223 and 5.56 loadings, some of which purport or are reported to be “Mil-Spec.” As part of the comparison, Jonathan looks at the pulled bullets, powder composition, accuracy, velocity standard deviations, etc.


While the testing methodology still has some holes in it (all were using the same barrel, which various loads are known to like some barrels over others and he discounts “flyers” which are often actually part of the base accuracy), the conclusions and results are still real-world applicable.

The ammunition tested includes:

  • Federal “American Eagle” AE223 55gr .223 Remington
  • Federal “American Eagle” XM193 55gr 5.56 NATO
  • IMI M193 55gr 5.56 NATO
  • Independence XM193 55gr 5.56 NATO
  • PMC X-TAC XP193 55gr 5.56 NATO
  • Winchester Q3131 55gr 5.56 NATO
  • Wolf Gold .223 Remington

Check out Jonathan’s article on his website here. The results are interesting including the solid performacne of ammunition that is not as highly “rated” by the internet community.

Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • BattleshipGrey

    He seemed to be quite thorough. It seems that it’s mostly going to come down to preference since they all seem to be performing about the same. I was a little surprised by the IMI accuracy, but as he said, it wasn’t really a true accuracy test.

  • UninfringedTech

    Does anyone know what hand stop is shown installed in the picture above? It looks uncomplicated and light.

    Disregard-found it in authors thorough review of his setup!

    • Sam

      Can’t beat BCM products.

  • gunsandrockets

    Most of those rounds ran faster than I would have expected from a 16 inch length barrel.

  • He noted that the accuracy was appalling. Well, you are shooting with a Red Dot and not a Magnified Optic with a reticle that will allow you to precisely quarter the bullseye and make a precise shot… So there’s that. And even rested, the gun was not sandbagged. So human error comes into effect. Those two factors tell me that the accuracy information can be discounted. Not tossed out completely… but discounted.

    • LegMeat

      I’m not disagreeing with you but would like to point out that J. Ocab is a Distinguished Rifleman and accomplished Highpower Competitor so he knows a thing or two about rifle shooting. Him without sandbags is probably stil better than a lot of people with them.

    • Paul White

      the one he referred to as appalling had something like 1.5-2x the size of all other groups…that he also shot those with red dots

  • nova3930

    Interesting that the XTAC is down at 223 velocities while the wolf gold is bumping up into 556 territory. I’ve always drifted towards 556 labeled loadings but may have to reconsider that….

    • wysoft

      Wolf Gold is Taiwanese M193, and I’m still not sure why it’s sold as 223.

      • nova3930

        That’s even more interesting. That’s a heck of a value in a 556 load. They’d probably sell even more if it was labeled as such

      • Blue Centurion

        Huh? I thought Wolf was a 100% Moskal ammunition. Are you thinking PMC?

  • Sam

    Lol yeah that watch? No thanks. That 1911? Looks awesome but it’s ridiculously priced, as well.