I have 24" M2, tried about all choke sizes made for it.
.555 Indian Creek will do 300 plus all day.
.562 will do around 300 with a little bit more forgiveness.
I like the Indian Creeks because they are the most consistent gun to gun.
About any choke .555 to a full choke with tss will get you a pattern that will kill way past what we should be shooting at turkeys.
I would skip the forcing cone work. Use that money for more shells.