Too, at least in Ubertis, the magazine tube is quite large for the 357 magnum, resulting in a sort of spiral orientation of the rounds in the magazine, rather than a linear stack. This in turn results in a stack in the tube where the noses of rounds don't line up with the primers of the round in front of them.
I still wouldn't load spitzer type bullets, but I would not be concerned about round nose bullets detonating in the magazine.