Ring around Aguila 9mm brass

That's a cannelure, used to help prevent bullet setback in this case. I've found 2 distinct kinds in Aguila 9mm. The "cosmetic" kind, that has no noticeable impact on the case interior. I've found no effect good or bad from this type. Yours appears to be the cosmetic type. I've also encountered a type with a deeply impressed cannelure which is reflected by a visible ring on the inside of the case. You can feel it when you run the expander into the case. These create a bulge in your brass if the bullet is seated deeper than the ring. I toss these in the recycle bucket.

After the rounds with a ring have been fired and sized I think they're all cosmetic.

Most of the federals I have loaded had that ring, I just loaded them.

No need to toss them out. They are as reloadable as any other brass boxer-primed cases.

The ones I had that were "bad" also had crimped and sealed primers. They really were unloadable with standard components. The cannelure didn't have the knurled look, but was a solid impressed ring. I believe the inside of the case may have actually been stepped also. The OPs case pictured appears to be the innocuous cosmetic cannelure. Load away!

Stepped cases are a no-go. I haven't come across many in my brass scrounging, luckily.

Yep load em and send them. The crimped brass is usually military. And it's darn good brass. I swage the crimps on them. The stepped ones just drop the charge to starting loads. I loaded many of them. Never had an issue. I mark them with a black marker. So i don't miss them for the next loading.

In the last 6 months, I’ve been experiencing higher than usual Shockbottle failure rates with Aguilar nines. Some gage fine, others don’t....so off to the dumpster they all go.

I like the ring, it makes it easy to identify them. They are very good brass to reload.

As said above, I've found several makers who put a ring around the case. I think Remington used to as well, but I'd have to dig to be sure. Anyway, I don't think there is a function associated with these rings.

FWIW, I don't gauge any of my semi-auto loads, I plunk test and get 99.9% good feeding ammo, mostly nothing to do with case manufacturer (except stepped cases and Amex). Early on a cannelure on a case was for preventing bullet set back, but today it is more often used as identification. If your OCD is acting up you can sort them out, but no need to treat them any different than any other brass...