Im actually not trolling. I have done this several times in my games. I have tested it twice today just to make sure. Ranged barracks do not have backdoor protection, you dont need creeps around to destroy it and they dont even regen.
At this point Im actually not sure if you are a fucking troll. But I will say again, do exatly what I did in a lobby. Destroy tier 3. Let the creeps push out and go back in. You dont even need items. You can damage it and it won't regen back up. Even if it says it has backdoor, just attack the fucking ranged barracks and see for yourself.
I do this a ton of times in the games, since its very easy to go back after you only manage to destroy tier 3, and take the ranged barracks down at least. THey are not the most important of the two, but you dont need creeps around to do it.
Not really sure if you are a in fact just trolling. If you are, congrats, you fucking got me. If you aren't, may the gods have mercy on your stupidity. Just do exactly what I explained in the previous post. Go mid, faster to push, buy items just to take the towers quickly. Then drop all of them, just so you see its not because you are 7 slotted. I was level 25, no items, and I destroyed the ranged barracks with no items. I'm telling you, do exactly as I said, and you will learn something new today about this game. Again, I have done this lots and lots of times during actual matches.
But you think whatever you want to think bro. Only gives you an advantage to assume that.