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Editor’s Note: This article on .223 vs 5.56 comparisons is an excerpt from Gun Digest 2013, the world’s greatest gun book.
.223 vs 5.56: A History
To a whole lot of shooters, ammo is ammo—if it fits, it shoots. These shooters tend to be the guys with seriously tired, worn, or even busted firearms. They also tend to focus on the wrong thing; you know, the guy who scrubs the brass marks off his ejector lump, at least until one day his rifle stops working or breaks into many pieces.
Ammo is not ammo. And when doing a .223 vs 5.56 comparison, while the loads are almost identical, they are not the same. To know why, we have to go back to the beginning.
The early 1960s were an interesting time. The returning GIs from WWII and Korea had a decade to get things the way they liked. Two tastes they acquired during that time were varmint shooting and benchrest. Varmint shooting was simple. Various members of the rodentia clan, going about their usual business in a field or pasture, served as animate targets. They were prolific breeders, there was no limit, no season, no quitting. You could shoot all day if you wished. Well, as much as shooters then and now like to shoot, shooting varmints with a .30-06 was just silly. The recoil would beat you up, the noise was alarming, barrels got really hot really fast, and the cost of ammo, even back then, was just off the charts.
So they went down in caliber until they found that various rifle cartridges using .224-inch bullets did the job nicely.
Benchrest shooting was a refinement and variant of target shooting. Instead of trying to coax all the shots into a 10-ring, the group was the score. The smaller the group, the better the score. Again, smaller was better, and the common .224-inch diameter bullet served well.
The premier cartridge in the early 1950s, when varminting and benchrest got started and began revving up, was the .222 Remington. Introduced, in 1950, in the Remington 722, it was superbly accurate, and the rifle was also a brilliant out-of-the-box shooter. The mild recoil would not cause a benchrest shooter to have aiming problems, and the mild report, efficient powder charges and low bore erosion made it a useful varmint cartridge.
For those who needed more reach in the varmint fields, Remington came out with the .222 Magnum in 1958, offering 2-300 fps more velocity than the little .222.
Now we shift gears from varminting to the on-going soap opera of the U.S. Army rifle situation. Having spent a decade and millions of taxpayers dollars, the U.S. Army Ordnance bureau has brought forth … an improved M1 Garand. And so screwed up is the process that they can’t even produce rifles quickly enough to arm the U.S. Army in any reasonable time frame. I once looked into the numbers and came to the conclusion that, at the rate the Army was buying and building (the U.S. arsenal at Springfield was still open then), the entire U.S. Army would not have been switched over to the M14 before the bicentennial. For those who don’t remember that occasion, the year was 1976.
So, the Army finds, in the mid-1960s, that the Armalite rifle is one that could actually be forced upon them. They pull out all the stops and do everything they can to prevent this. “Real men shoot .30 rifles” was the prevailing ethos of the day (and in some circles, still is).
The cartridge the Armalite rifle was chambered for was the “.222 Special,” a case halfway between the .22 Rem. and the .222 Rem. Mag. It also split the difference between them in velocity. The Army, recognizing an opportunity, first accepted the velocity as sufficient. Then they upped the stakes and insisted on better and better down-range performance. Basically, they kept asking until they had exceeded the pressure limits of the .222 Special. But the problem is that pressure is not simply velocity-dependant. Still, the designers had managed to meet the velocity specs, and the rifle was adopted.
I have now, in less than 700 words, summarized years of work, 100,000 man-hours of engineering, manufacturing and range testing, and we’ve only begun.