How do you make blunderbuss ammo in red dead redemption undead?

Answer 1

I just got it and yeah like the other guy said you open coffins also you search undead corpses and when you save towns you get some ammo as a reward along with a new weapon and around towns under attack there are boxes marked as green circles you go to them and open it .

Answer 2

you have to make it in your kit

Answer 3

Kill undead