excellent experience w/"training" steel case in 75 grain
+1 Kwanger
I picked up 1000 rounds of this steel-case Hornady "Training" ammo, but mine was 75-grain BTHP; it's labeled .223 rather than 5.56. Price was $239 plus Austin sales tax, over the counter. 20 white boxes of 50 rounds each in size; I've shot maybe 170 rounds of it, and like it in my 8:1 20" heavy Lothar Walther barrel.
Group size at 100 yards shrunk to about half the size of the Golden, Silver and Brown Bear 62-grain I'd been shooting -- 5 shots of Hornady averaging between 1 1/4 to 2 inches, one about 5/8", compared to the Russians at 3 to 4 inches, with some closer to 5". So under identical range conditions, the Hornady was easily twice as accurate. Monarch brass Croatian .223 55- and 62-grain was noticeably better than the Russian, but not close to the Hornady. At 0.24 cents per round, compared to maybe .20 for the Bears, the Hornadys are very satisfying.
This was on a table, with a stubby bipod, and a sandbag under the rear stock. Stools provided were only adjustable long ago, and all are shorter than I'd like, so not a perfect situation, but pretty good.
A friend gave me a box of pricey Federal 77-gr LE rounds; these were the $1.50 a pop kind. They were in fact better than the Hornady budget training ammo; one group of three was all touching, and two were more or less an inch. (The other two had one rogue in each, and I know each one of those was me.) That kind of stuff isn't in my budget.
But a friend got me reloading. That's another world all its own, and even my early efforts look comparable to the pricey Feds, actually better. And a little cheaper yet; I'd been saving brass for a year, and so didn't need to buy any right away.
So, in order, in my gun, more or less:
Bears 3-5" Brown, Silver, Golden were frustratingly similar.
2 1/2 - 3" Monarch 65 grain BTHP
1 - 2" Hornady Training 75 grain Training BTHP
<1 - 1 3/4" Fed LE 77 grain BTHP
<1 - 1 1/2" Handloads 68- and 69-grain Hornady or Sierra match
Handloads rule, though: more groups on the smaller end. I am not a deadeye; even with the bipod, some of the variance is me. I am about to try 75-grain Sierra match bullets, which others have said are a nice weight.