Actually the holding the gun sideways was a practicality thing. When unloading a magazine rapidly you have limited control of the weapon's recoil. When holding a gun upright the recoil moves it upwards, holding it sideways moves it sideways.

Now imagine you're a gangter, 'bout to come up on some punk steppin' on your turf. You an da boyz gatted up ready to throw down. Get in the low-rider with your illegal Tek-9. Roll up on those fools ready to shed lead. Which way do you want your recoil going? Upwards? Or sideways.

Rat-tat-tat.

Maybe the difference is parliament. A dictatorship will have advisors and may delegate limited control to other entities however they are the 'final word' and the only opinion that cannot be circumvented. Traditional monarchies would have also been dictatorships. Modern monarchies delegate significant power to parliament in manners that can't be circumvented by their own will. So I'd say that the difference between a modern monarchy and a dictatorship is a democratically elected parliament that has power beyond the will of the monarch.