The rules for the Stand and Shoot charge response say that in order for a unit to stand and shoot at the charger, the charging unit MUST start the charge move more than it's own move stat away from the target unit.

For models that have a random movement such as the hell pit abonamation can you use the stand and shoot responce since the abonamation is always within its move distance for charging.

The only charge reaction you can make when charged by a unit with random movement is hold as the unit with random movement cannot declare a charge like normal units (p74 of the rulebook), this also means you dont have to take a terror test when the A-bomb rushes you (p78).