They were armed with bows
Much used in war in those times: and could use both the right hand and the left, in hurling stones, and
shooting arrows out of a bow;
they were ambidextrous; who could sling stones, or shoot arrows, with either, which was no small advantage to them: even of Saul's brethren of Benjamin;
they were of the tribe of Benjamin, of which Saul was, and so his brethren; and they might be, at least some of them, his relations and kinsmen; who observing the unreasonableness of Saul's enmity to David, and detesting his cruelty, and sensible of the innocence of David, and of the service he had done his country; and perhaps not being ignorant of his divine right and title to the kingdom, went over to him, to comfort, strengthen, and assist him.
The Brenton translation of the Septuagint is in the public domain.