One of the biggest issues I have with groups is their willingness to actually engage in social interactions, whether with other NPCs or each other (mostly they're run via messenging services, thus people are more open to characterisation). In Dark Heresy, Deathwatch and such this isn't much of an issue due to there not being much of a an authoritarian structure hanging over the heads of the players directly. Acolytes are usually equals operating amongst themselves, Explorers are expected to advise and speak with the Rogue Trader, Deathwatch Marines are… well, marines, Chaos Heretics are- uhm, well, what do they care when they need each other?
With Only War however, players always seem to be incredinbly reluctent to open their mouths, for fear they'll invoke "NO TALKING!" by an NPC such as a Commissar, a superior officer, or even the Sergeant character. Doing down time this is less of an issue, but I find my players just turning into dice bots whenever they're actually out in the field, especially alongside their fellow regimental soldiers. They don't have this issue in other games and despite my efforts at OOCly encouraging them, nobody really seems to budge. Its not so much they dislike actually roleplaying Guardsmen - they have done soldiers well in the past - but they seem mortified to do it for suffering IC reprocussions. Its realing killing my efforts to actually GM this, as well as my players enjoyment.
Any ideas? How have you got more roleplay into Only War?