Ill give you a quick insight into how I build my 4beting range in this spot. If some of this stuff is unfamiliar please ask about it, I would be happy to explain it.
First thing. I don't like cold calling a 3bet. We give up being the aggressor in a big pot and I don't like doing that. So in this spot, I am cold 4betting or folding.
I'm going to assume 100bb stacks and something Like this:
- MP opens to 3, CO 3bets to 9, Hero(BTN) 4bets to 24, MP folds.
CO needs to call 15 to win 37.5 ( Blinds(1.5) MP Bet (3) + CO bet (9) + Hero's bet ( 24).
the price we are laying CO is 2.5 to 1. Which means that for each value hand we have we want at least 2.5 bluffs.
The range I built in the lab is: QQ+ AK, AQ, A2s-A5s. This range gives us 18 combos of value, 48 bluffs. Close enough for me.
I selected A2-A5 as bluffs because they block AA and have ok equity when we get called by hands like JJ-KK.
Note this is assuming that CO has a decent 3bet %. If he is only 3beting 2% I'm only getting in this hand with KK+
The point of the range that I built is to essentially steel the pot. If CO is only 3betting the nuts, we are not going to steel the pot.