Are we held sinful or do we owe expiation for having shipped weapons to Muslims, which led to aiding in the bloodshed of some of them, knowing that we delivered them to military councils?

The fact that the ultimate use of a weapon is unknown, and it might fall into the hands of someone who uses it for an unlawful purpose, does not change the ruling. This is because the consideration is given to the present state (al-hal) and not the eventual outcome (al-ma'al), and to what is common (al-ghalib) rather than what is rare (al-nadir). This mere possibility does not place sin upon the one who manufactures or transports the weapon for a permissible purpose.