It think it actually tear off limbs. The 50 BMG supposedly has anti material capabilities (meaning vehicles, light fortifications maybe).
I think 60% of bmg is grossly overestimated. Just looking at energy levels on a few velocities on wikipedia, the 06 shows as having just under 3000 ft-lbs.
The BMG has between 13,000 and 15,000 ft-lbs (according to wikipedias numbers)
I don't know about vapor trails. I have seen a few videos on youtube a few years ago back before they started censoring war videos of insurgents being shot up. They were in tact, but not fully, if you know what I mean.