Pretty neat offering in 556/223.

Yes, as I stated in your other ammo thread. But I'll go into more detail here.

For the price of roughly 40 to 50 cents per round (from SG Ammo's site), their "match" ammo is a decent price. I don't feel it's true match grade, but it seems to shoot more accurately than other brands at this price point.

I shot their 55 grain HP match in both 223 and 5.56 NATO versions.
24" 1/8 twist barrel did groups of 1.4" to 1.75" with the 223, and 1.25" to 1.4" with the NATO.
16" #2 1/8 barrel did 1.0" to 2.1" with the 223, and .9" to 1.3" with the NATO.
16" #3 1/8 barrel did 1.1" to 1.8" with the 223, and .9" to 1.1" with the NATO.
14" 1/7 twist barrel did 1.9" to 2.3" with the 223. Did not test NATO.
All these barrels have 5.56 chambers.

I shot their 62 grain JP match in the 5.56 NATO.
24" barrel did groups of 2.5" to 2.9"
16" #2 barrel did 1.5" to 1.6"
16" #3 barrel did 1.9" to 2.5"
14" barrel did 1.4" to 2.6"

I also shot the Frontier 68 and 75 grain loads. They generally performed worse than the 55 and 62 grain listed above.

For me the 55 grain match loads produced reasonable accuracy, but not up to the standards of my other match ammo. From the limited testing I did on steel at 200-300 yards, I saw Frontier's accuracy degrade more than I had expected.

I honestly don't have a burning need for Frontier ammo. If I truly want precision performance from my ARs, I'm willing to pay the additional $.25 or so per round for the likes of FGMM 69, Hornady 75 HPBT match, or Hornady 55 VMax. A reasonable cost savings is Hornady's Black 75 HPBT, as it's accuracy is really close to their 75 HPBT match. If I don't need accuracy -- say, for close paper targets in run-and-gun carbine matches -- AE223 fills the bill at a lot less than Frontier.

Frontier may work for you, however. Frontier's 55 grain match ammo will certainly be more accurate than the FMJ you've tried.