Well, listed case dimensions are the same, and each will chamber in barrels bored for the other.
But thats not the full story.
Service loads for the 5.5645 NATO generate 58,500.
Do you own an AR like this SAINT? Do you know what ammo to load in it?
Roughly .125 more freebore, say the white-coats bearing micrometers.
Can You Shoot .223 in a 5.56 Rifle?
The reverse .223 in a 5.56 chamber doesnt have the same pressure concerns.
Are they the same? Here the 5.56’s crimp distinguishes it (at left).
So what does that mean for your firearm?
.223 vs. 5.56: Fraternal or Identical?
Working with Gene Stoner, Bob Hutton atGuns & Ammomagazine paired a 55-gr.
Popular 55-gr. loads can shoot well from a 1-in-12 twist. A faster spin helps with longer bullets.
bullet with a case a tad longer than a .222s cartridge case.
The tiny missile exited at 3,250 fps and met a retained-velocity spec of supersonic flight to 500 yards.
In 1980 it earned the approval of NATO nations, which substituted an FN-designed 62-grain SS109 boat-tail bullet.
The .223 is a relatively short cartridge designed for more compact rifles. It is shown here with the larger6.5 Creedmoor.
The SS109 left the gate at 3,100 fps.
Itssuperior ballistic coefficientensured harder hits at distance.Faster 1-in-7 rifling twist maintained accuracy.
The U.S. Army called this load the M855.
Tiny groups like these are very possible with quality ammo and a good rifle.
By then, case length in millimeters had joined the moniker.
So was born the 5.5645 NATO.
It was soon recognized that the round had a lot of merit for use in sporting rifles.
Black Hills Ammunition tests 5.56 loads for terminal performance in gelatin, as well as for accuracy. Image: Black Hills Ammunition
The .223s design owed much to the popularity of the .222 Remington round that had been introduced in 1950.
The triple deuce cleaned up at Benchrest meets and bumped pelt counts for fox hunters.
The .223s 1.76 case is just .06 longer than the .222s.
But the .223 has a shorter neck and holds 20 percent more powder.
A tiny rodent behind the crosswire demanded fine accuracy not required on the battlefield.
An infantry rifles priority wasfunction, often in trying conditions hunters didnt endure.
As a result, M16s got generous chambers.
Bolt-action rifles enjoyed tighter tolerances, shorter bullet jump and slower 1-in-12 rifling for popular 40- to 55-gr.
But, todays ARs in the civilian market have proven to be extremely capable of impressive accuracy as well.
Winchester alone lists 18!
So does Hornady, from a 35-gr.
NTX bullet at 3,760 fps to a 75-gr.
Superformance Match BTHP at 2,930.
Federal catalogs a dozen .223 loads, including a 60-gr.
Nosler Partition at 3,160 fps and a 62-gr.
Trophy Bonded Tip at 3,050.
Swift loads a 75-gr.
The .223s credentials on prairie dogs and coyotes hardly need defending.
But where its legal for deer, hunters debate.
Two-two-three acolytes dig out ballistics charts.
The .44-40 has laid low countless deer with 200-gr.
bullets that bring 450 ft-lbs to 100 yards.
7mm Magnum bullets on elk!
Arguably, precise shot placement matters most with small bullets.
The wide range of .223 loads begs sifting before you specify rifling twist.
Nosler advises a 1-in-12 spin for bullets no longer than its 60-grain Partition.
As always, test out your preferred load in your gun to check results.
Much like the7.62 and .308 rounds, there is sometimes confusion over what each cartridge designation means.
Are they the same, or are there significant differences.
And now you know what you could shoot in which!
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