Gun screwdrivers are ground so that the sides are parallel where they meet the end. Unlike most cheaper workman screwdrivers which are taper ground to the tip. Screws are slotted with parallel sides, which is why the typical tool box or household screwdriver damages them - they wedge the sides open wider at the tip, creating a ridge, and because they often don't fully seat or fill the gap between the sides of the slot, twist out when the friction of the threads is higher than the friction holding it in the slot.
Given a choice between a screwdriver out of the kitchen drawer or the magazine, I'd use the magazine. It's a better fit and it's actually meant to be used that way.