MW5 is weird because there are two separate rolls for salvaging, and you need to pass both. The first one is 95% likely to succeed if you get a headshot, so that's fine, but then you have to roll again and the second one only has a 60% chance to work. So in the end headshots only give you a 57% chance to salvage which is pretty shit. The second roll really fucks you and there's no way to improve its odds without modding.
If you kill by CT or legging the first check is 40% so the overall chance is 24%, if anyone was wondering.
Also MW5 has salvage shares which can make things weird. If you get perfect headshots and leave the rest of the mech untouched then it has a high value since it's in nearly perfect shape, so you might not have enough shares to salvage it. If you're more sloppy and end up destroying both side torsos and a leg before taking the head off it's worth way less, so you're far more likely to be able to afford it. Which makes sense, but it's still weird. You end up with scenarios where you see a mech you want to salvage, so you deliberately damage it before headshotting it so you'll be able to afford it on the salvage screen. I mean, assuming it shows up on the salvage screen, because you still have the 40% chance it magically vanishes because fuck you.