223 5.56×45 Ammo 55gr FMJ Federal American Eagle (AE223BKX) 1000 Round Bulk Case

federal american eagle

comparing Federal American Eagle 5.56 XM193 55 grain FMJ ammunition to their 223 Remington AE223J 55 grain FMJ load. Since a good many AR owners shoot one or both of these varieties, his results might be of interest.

I have shot a good deal of both through three different ARs. I can usually find the 223 Rem ammo for about 5 cents per round less ($1 for a 20 round box) when purchased locally at Academy Sports. The rifles I have shot these with are a Ruger AR556 carbine with a 16″, 1:8 twist barrel and a 5.56 NATO chamber, a PSA with an 18″, 1:7 twist barrel with a 223 Wylde chamber, and a Colt LE6920 carbine with a 16″, 1:7 twist barrel and a NATO chamber.

I have personally seen no significant difference in either POI or accuracy with these two loads at ranges up to 200 yards with any of the three rifles. I have not had an opportunity to shoot them back to back at longer ranges to judge if there is any difference at longer ranges.

Harrell uses an M16A1 with a 20″ HBAR 1:7 twist barrel with a 5.56 NATO chamber. Although Federal lists a slightly higher muzzle velocity for the 223 Rem load, when Harrell chronographed the two through his NATO-chambered rifle, he got a muzzle velocity a little over 100 fps greater for the XM193 load. Of course, Federal probably tested MV of the AE223 with a test barrel with a 223 Remington chamber, and the slightly tighter chamber might have produced a bit more velocity. But Harrell saw no significant change in accuracy or POI at 100 yards.

federal american eagle

I pulled out one of each of these cartridges from a fresh box and examined them. Yes, there is a clear difference in COAL between them, but my caliper measures a difference of 1.2 mm rather than the 2.0 mm Harrell quoted. Looking at the projectiles, I can’t see an easily visible difference between the ogives. The .223 Remington projectile just looks as if it is seated more deeply in the case. But if you go to the Federal website, you find that they list different ballistic coefficients for these two FMJ-BT projectiles: .246 for the 5.56 and .269 for the .223 Remington. So presumably there is some subtle difference in projectile shape.

As for the difference in muzzle velocity, Harrell observed a difference of 116 fps which was a gain of about 3.8% for the 5.56 over that of the .223 Rem. That is not a huge percentage gain, but possibly significant for some applications. I am no internal ballistic expert, but since the 5.56 cartridge headspaces on the case shoulder a 1.2 mm shorter cartridge means a longer freebore for the projectile to jump before it engages the rifling of the bore, and more free chamber space overall. So my guess is that could diminish peak pressure at least a bit.

The slightly better G1 coefficient for the .223 Rem projectile might account for the fact that these cartridges shoot to the same POI at 200 yards despite the lower muzzle velocity of the .223 Rem cartridge. I plugged the muzzle velocities that Harrell got for these two rounds and the ballistic coefficients given by Federal into a ballistic calculator. With a scope zeroed at 100 yards, the .223 Rem impacted only .24″ lower than the 5.56 at 200 yards, .70″ lower at 300 yards, and 1.2″ lower at 400 yards, really not much difference practically.

As cowboy 1964 points out, neither of these cartridges are going to be the best choice for anything resembling precision shooting, especially getting out to medium ranges greater than 200 yards, but a lot of people do shoot this stuff, and for some folks it is all they shoot. I have known a lot of people who pay more for the 5.56 “NATO” cartridge instead of the cheaper .223 Rem cartridge under the assumption that it is more powerful, more accurate, or just “more better”. And indeed, for any application that either of these cartridges might realistically be used for, there doesn’t appear to be any practical difference whatsoever.