Not to stray off topic too much, but to clarify, I think Luke S is talking about these https://rokslide.com/forums/threads/ultralight-ultralight-rifles.329402/ not a gasser AR. They don't have the same (potential) issues of what you're describing. And as for being fragile, if done right, they aren't, by any stretch. My Montana (stock) has proven more fragile by far.Awesome that you've found a rifle to take hunting for bear this year.
However I would advise against the ultra-ultralight AR. I run tactical rifle and pistol courses as my side-gig and I have seen way too many reliability issues with the super ultra rifle that have came to the classes. Some of those have been minor, like failure to feed or light strikes, but quite a few have been major, like BCG's bulging or cracking and gas blocks blowing out.
But don't let that complete dissuade you, you can easily build a reliable AR that falls right around 5ish pounds.