I took a few shots with them and they seemed ok but Henry says to never use aluminum or steel in their guns. I will stipulate that brass is King, but for slow firing is aluminum all that bad?
Looking for opinions but also practical experience.
I'm going to presume here, so take it for what you paid for it.
Brass receivers are, relatively speaking, softer than steel. Meaning if you rubbed steel and brass cases across it, the steel cases will cause more wear in the same amount of time. Related to that, Steel cases are often times coated in some form of coating, which IME, is not typically a hard and smooth substance. This means that you can embed grit and grime, and create your own lapping compound. Especially if it is gritty and not clean, that can further agitate any sealing issues with lesser quality ammo. Again flame cutting going backerds into a brass mech, isn't an ideal situation.
Shooting a few boxes of that ammo through the rifle, isn't likely to cause the decline of western civilization. Fed a lifetime of less than ideal ammo, given the considerations above; will cause faster than normal wear to occur.
For eons now, the AR scene has been filled with tales of woe for anyone who durst shoot steel ammo in their rifle. Of course not a single one of them can ever give you anything other than an anecdote, or a story about a brothers-sisters-roommate who once talked to a guy in a gas station..... I've worn several barrels, in both bolt and semi automatic rifles and pistols. The chambers were never worn abnormally quickly, but the propellant used in some of the "economy" ammo, can definitely be a little hard on the gas ports.