In the movie there is a scene where they ?confiscate? weapons from a retreating infantry unit. I believe this was based on fact.
I just watched the entire series and never found the scene you are describing, prior to going to bastogne they did take any ammunition that retreating infantry soldiers were carrying because they were short supplied as it was and the mentality of a paratrooper was that you did not have supply depots so you better carry as much as you can because it's all you have.
similar instances were reported on both fronts of the war. Marines still using 1903 springfields in the south pacific stole crateloads of M1 Garands from Army supply depots.