I too own one of these monsters, and love it very much. But I have learned not to offer to let everyone shoot it! I have seen the double fire a few times, with one of the people being my own 250lb. gun loving father! Now I make sure that all shooters have enough experience, and since I reload, I slowly work them up the scale of power.
Since I do reload, I like to make many different loads for this gun, But in my experience, you cant always trust load data! I too have made those rounds that (DONT IGNITE)! That is a very spooky feeling with this beast! And that was load data from a VERY respectable source! They have since corrected their recipe, but I have to wonder how many people found out the hard way?
I am still a little spooked every time I make a new batch of ammo, as I have had the most problems finding load data for the .500, and fear very much ever harming myself or the gun, its just so powerful, I could only imagine the damage. I have also heard about problems with bullet slip during recoil with the .500 bullets but have never experienced it. I bought the hornady dies that have the extra taper crimp die, and even as a novice reloader, I used the extra die and have never had a bullet slip yet, but now I keep an eye on all these things! Yeah its alot to worry about, But very rewarding when it all works right.
With all that said, just make sure if you own one of these, just use your judgement on who fires it, and make sure they know what their in for, that way we get to KEEP these fine hand canons!

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Omiedudeman