First let's all take a moment to make fun of "assault rifle version." (long pause for laughter)
Next let's try to remember LG is an idiot on the topic. (Sorry LG, don't take it too hard, I'd be useless in a conversation about M Theory) So let's not beat him up too much and explain practical vs functional differences.
LG (or whomever needs to be paying attention here) you neither need to know or care about the differences between direct impingement vs gas piston yada yada firearm gack. What you and yours need to grasp is that ALL of the rifles (outside of, you know, actual assault rifles) work on the idea of one round per trigger manipulation being fed from a removable box magazine by cycling of the bolt via the gasses or recoil of a fired round. Such rifles have been available to the American public for nearly 120 years now. That's the functional part. Whether civilian from the outset or "civilianized" versions of military designs makes not one jot of difference.
The practical difference is like the design with anything. We'll stick to the AR platform since that's what you mostly find here in the US. That design was made to be modular and extremely flexible, which is just another way of saying it's customizable as hell. Being based on long standing military specs every component is made by all kinds of people and "different" guns from varying manufacturers can have parts replaced or upgraded from numerous companies. Then there's the ability to swap out uppers on the same "lower" which allows you to literally take a short barrel of one caliber and swap it out with a long barrel of a different caliber. This is what makes the AR platform so appealing over others from a practical standpoint.
So to recap;
Every single thing as a matter of function is same.
Individual aspects between firearm platforms can be different and have little to no bearing whatsoever on the function.