I am not up on gun safes, so I cannot say.
I agree that 750 pounds is pretty hefty. I suppose if it is adjacent to an outside door that leads right into the driveway, someone or two with a hand truck may be able to move it, I know it is nothing I could move, unless the guy helping me can do it all on his own. I could handle 50 pounds, he would have to handle the 700 plus weight of contents.
No matter what the weight, if I had one set in place, I would bolt it down for good, just for good measure.
If on a concrete slab, a decent rotary hammer will drill four holes in less than fifteen minutes to anchor the bolts down using an achoring cement in each hole.