I read the Lucky Gunner report several times because I already had an investment in several cases of the 55gr 223 stuff, and I had both basic and precision rifles to shoot it out of. I wanted to be certain I wasn't going to screw up any decent barrels of my own.
Rear and rereading, and weighing both LG's and my own conclusions, I determined the following.
The most significant point of wear was the extractors. The steel case stuff was especially unkind to the basic AR extractor. I just recently replaced a broken extractor. It was a ten minute job with basic tools, and the parts cost, even using upgraded parts, was nearly negligible.
Bore wear with the 'steel case" was more significant. But, the firing cadence was rapid, far more so than I would have ever done with any ammo in any AR I own. The report noted this and cited this as a factor that significantly accelerated bore wear by both types of ammo, but especially with the "Steel case" ammo.
Let's stop a moment, and examine this 'Steel Case' ammo. The term is misleading; nearly a misnomer, Yes there are components in the metallic jacket that are contained in what is commonly called steel, but the formulation is important, and that which is present in Steel jacketed ammo is so different that I would personally prefer to call it "iron core" jacket material. Its very need to be ductile and malleable makes it almost diametrically different from what most of us mean when we say "steel", as in Tool Steel. Many of us would be surprised to find out that during WWII, just about every one of the powers used these steel jacketed bullet, including the USA. There were literally millions of rounds of steel core 30-06 produced by the US during WWII.
I have the stuff, that doesn't mean it's my first choice. It's my last choice, my "back's against the wall" choice; the choice I use when it's me or the barrel, buddy. Some of you might make that same choice. What pretty much all of us (the ones in our right minds, anyway), would not do is multiple absolutely fastest possible mags dumps with the stuff. It has a place in our viewpoints, and that's not it.
It's OK, IMHO, for plinking, especially regarding cost. It's something to keep on hand for when you can no longer afford to send the every best, and if you don't send something, the game's just plain completely up. It has its place, it's just not likely to ever be first place.
At my house, there's a rifle reserved for its use on a heavier than usual scale. Sitting directly next to that rifle in the gun cabinet is a brand new identical replacement barrel.
Over the recent years here at The 'Hide, we have come to the recognition that barrels are wear items; parts with expected life spans, with an expected eventual replacement in their futures.
So I'd say, if we must be Nervous Nellies and shy away from things like steel jackets, let's of course do so.
But we don't all have to do that.
Greg