Murtaugh should've unloaded the gun before he gave it to Riggs.
Just imagine if he shot himself instantly.
shareRiggs would have seen him take the bullets out. Also at that moment he was fairly sure Riggs was full of shit and was going to back out. As it turns out he wasn't full of shit and Roger blinked first.
shareGood thing Roger did “blink first” by grabbing the gun when he did
I didn’t notice my first viewing, but Riggs actually pulled the trigger
I’m guessing Murtaugh saw it in his eyes - that final close-up where Riggs went from crazy to suddenly calm