Sometimes people set off my claymore but live through it. Is there a perk to help survive explosions from equipment, or is this simply my placement?
Any tips for better placement?
There are two main perks that help counter claymores.
1: Flackjacket - this perk limits explosive damage taken. If someone has this perk then there is no way a claymore will one-hit kill them. Unfortunately there is nothing you can do against this. I would recommend motion sensors if this is a problem for you, as motion sensors have no "counter".
2: Lightweight - this perk increases your running speed. If the claymore is badly placed then it is possible to run through the blast zone and avoid taking full damage. This can be countered, however, with good placement. When placing your claymore you have to remember that the explosion comes out from the front of the claymore, i.e. it is not omni-directional like a frag or a semtex. You also need to be mindful as to where the enemy is going to be running when they enter the room or area you're protecting. Place the claymore facing your enemies' chosen path, bearing in mind that claymores have a slight delay before exploding.
I would guess that your main problem isn't placement but instead Flakjacket. The claymores have much less delay then they have had in past COD games. This means that getting past them with Lightweight is a lot harder and less likely. If you're running into this a lot and it's getting you killed often, I would strongly recommend motion sensors or even the camera. The motion sensor in particular is a very strong choice as not even Ghost, a perk that blocks most things, can protect you from motion sensors.