That does pose an issue. It wouldn't if he had access to his own powers as well, but alas, that isn't the case. He takes a moment to study the guns, sizing them up. The technology here is different from what he's used to, so even he can only guess, but at least he has more to go on.

"The guns here use metal bullets. They're finite." These seem to be no exception, though they also seem capable of holding far more than the pistol he was given during their initial escape. "At some point, they will have to pause to reload. Or they'll stop to conserve ammunition once they realise they can't get through your shield. Wait for that opportunity."