Just remember folks: "AR" does NOT mean only .223/5.56.
"AR" (in modern vernacular) means "platform"!
I have an "AR" in .458 SOCOM that I use as a dedicated hog gun, but it could be used for anything that you would hunt using a 45-70.
There are many "AR" variants available...(and even more that could be wildcatted).
The AR is a very modular design. I might be using a .223 upper one minute....and by just pulling out two pins...I could swap on another "upper" (say...6.8, 458 SOCOM, 50 Beowulf, 450 bushmaster, etc) and hunt something else. It takes less than a minute to make the swap.
Some of the variants use proprietary magazines...but most do not.
This doesn't even include the variants that have sprung from the AR-10 (.308). Pretty much anything that uses the .308 as a parent cartridge (7mm-08, .243, .260, .338 federal, .358) could be used.
The only restrictions really...are the O.A length of the cartridge (needs to fit the magazine) and maximum pressure levels (should not exceed the original design parameters).
The sky is the limit for the AR!
Is it "traditional", I think not. Is it "practical".....Heck yeah!
Edit: add pics and commentary:
Nephew shown here holding my .458 Socom (rigged for hogs).
But… this rifle could easily be used for Deer, Bear, Elk, Coyotes, whatever.
Hand-loaders can shoot anything from a 100 gr. pill (yes 100) all the way up to 600 gr. solids.
Ask my nephew if he thinks the “AR” is a good choice for hunting: