Wow, I'm glad my parents didn't take some of these approaches when I was growing up. My brother and I always had the most realistic toy guns you could find, but my father made it clear that these were TRAINING AIDS. We played with them all time, shot a metric ton of those paper cap rolls, etc., but we weren't allowed to point them at any of our friends or each other. I got a BB-gun pretty much as soon as I could walk, I still have vague memories of my grandfather cocking it for me since I wasn't big enough. We got real guns as early as possible, and it was always treated as a system: shooting the REAL guns was the reward for handling the TRAINING AIDS properly. The one exception was water pistols, which even back then were pretty clearly NOT guns, even to a 4 year old.
Also, I was every bit as obsessed with guns when I was 3-4-5-6 years old as I am now. My parents didn't try to hide them from us or frighten us with painful negative reinforcement, they simply told us that any time we wanted to look at or handle the guns, all we had to do was tell them and they would unload them for us so that we could look at them together. I could look at and handle real guns anytime I wanted to, so there was no mystery in them for me. Guns were in view in most rooms of the house, but my brother and I never even considered picking them up without getting one of our parents first....why would we need to?