Sam knows there's no point in interrupting Bucky here, and he gets it. The need to try and do... something. Anything, really. He feels it in his cold, freezing bones, too. The door will not yield, at least not fast enough. And when Bucky uses his right arm, Sam winces.

He doesn't say anything, at first, even then.

But after a good long while of it, he gently calls out:

"Bucky... hey... Buck. C'mere."

his voice doesn't carry. But he knows Bucky's gonna hear it.

Despite all of his strength, he hasn't made a dent in the door.