Leave the buckshot for human targets. In the early 1980’s the Alaska Dept. of Fins and Fur tested buckshot vs. slugs on some brown bear skulls they had that were overflowing their HQ freezer. None of the buckshot rounds penetrated the skull and only about 1/2 the typical round nose slugs did - the others deflected off. Then they tried the then-new to the American market Brenneke slugs. They penetrated 100% of the time due to their sharp-shoulder design. After that “study” was published every LEO and fish cop in the state stoked their 870’s with Brenneke’s. So do I.
That is what use when the bears are awake, the hard cast, sharp shoulder Brenneke KO slugs. In winter when the threats are human or mountain lions I use 3” 00 Buck.
I had a one shot stop using a Brenneke slug on a 4” diameter Christmas tree. (It was raining and I was too lazy to fire up the chainsaw).