"You carry them." It wasn't that Steve was opposed to firearms, or reluctant to use them, he'd carried a pistol during the war, but as time went on he'd found that he was better in close combat, and he was good at using his shield when something ranged was called for. Disarming and disabling enemies, particularly when he felt less certain about their politics and position (truthfully, the lines between 'good guy' and 'bad guy' had started to blur a lot since the end of the war -- and looking back, Steve could even recognise the fact that things seems cleaner then because of the propaganda that he'd bought into and been a part of) and that made Steve feel even less interested in using potentially deadly force.
He might change his mind once he got a better read on the situation and what kind of environment they'd found themselves in, but for now -- he was fine leaving the crosshairs to Barnes.
Rogers wasn't sure why he did what he did next, but it somehow felt necessary, and he stuck out his hand for Bucky's. He knew there was tension in the air and he could certainly feel how wary Barnes was about what was happening and the fact that they'd both somehow found themselves in the middle of it. It was just that he felt the need to be grounding somehow, that he needed to put action behind words and give Bucky something -- a hand -- to hold onto as a way of showing that he meant what he said.
Or maybe it was something else. The first time they'd met, back when they were both a lot younger and Steve's knees were a lot more knobby, they'd agreed to look out for each other, and they'd shaken on it. Their friendship was based on an agreement, really, from day one that sometimes they needed sticking up for and there just wasn't anyone else around who was going to do it.