This is why I don't shoot cans on semi-auto guns except 22's. Fouled out in no time has been my experience. Good luck.
As in failures?
They get so dirty there's reliable cycle issues. I like simple things that I can rely on, so I use bolt and single shot guns for cans. They still get dirty but always function. Those who want to chase the gremlins until they get something reliable, more power to them. It's just not for me.
I get what you're saying, I really do. Historically AR's and I don't jive. However, I paid attention to the few guys around here that know them well. And, I've watched them in my hands, as well as people I am spotting for. And my number one takeaway is LUBRICATION. Ya gotta keep the BCG and action very wet with oil. So, having said that, again going off the guys that use them more than me, the homemade potion of 75% Mobile-1 5W20 and 25% ATF has served me very well. Now, admittedly after lots of rounds on the range, or lots of rounds into a sounder of hogs, I pull the bolt, wipe it all off, reoil, and reassemble. Since those steps have been performed the last few years, I've had almost no break downs, and this is shooting suppressed.
I call AR's female rifles, they are finicky and require more attention, but we gotta have em.