Maybe I'm blind or just don't remember reading the section, but if a player is currently engaged in an enemy in melee range, does prevent the marine from doing any actions other than melee subgroups? I know a character can disengage, or move/run away from the engagement provoking a standard attack- but is this the only situation? Can a marine who is in contact with an enemy still opt to make a ranged attack against a different target?
Also- thrown weapons cannot be used in melee (except as improvised weapons) unless stated correct? One of my players, the devastator marine, after being swarmed by a horde of cultists decided to prime a grenade in his hands. With his faith in the emporer, he was sure he'd take no damage (which he didn't, since frags have no penetration and he managed to roll low enough on the damage). Now- this may be a little unbalanced because he just simply destroyed the horde around him. Blast 5, + 1d5, +1 for explosive damage, +1 for armor bonus, resulted in him destroying 1 good 12 horde members, without resorting to melee (albeit with a small risk attached).
Is this a legal move? I know grenades use BS to throw and probably wouldn't be allowed in a melee engagement- but it just seemed to epic to pass up on.
Would love to hear some insight from other players.