Yes, CM resistance is it.
Hans in depends on target aircraft. If it has and CM and how it is installed. And also launch circumstances. All aspect can lock on from the front, but a bad angle can still cause it to lose track, or lured by a CM in the worst moment. In case of all aspect, mostly depends on CM resistance, and the number of CM res rolls the missile has to pass till the target. A long range IRM is far less effective with the same CM value.
What I learned, the the effectiveness depends on a lot of factors.
-First, reliability roll.
-Then lock on chance (same of above)
-Then the missile booster/sustainer values has to be adequate for the missile to be able reach the target.
---If it slows down in the terminal phase, it will be a lot more easily shaken off. (early AA-2 and Sidewinder)
---If it is too fast, the missile tracking rate or turn rate will be way too low for tracking. Basically the missile cannot scan fast enough, keep track of the target and still turn towards it.
-Tracking rate. it is something like how often the missile updates the target - if this is too slow, between two scans, the target can get out of the seeker FOV and lost. If too fast, the missile is unshakeable, follows ever little maneuver you make. You can only shake it if it has low Turn G, or runs out of speed.
-Turn G similar to above. if target position between scans have changed, the missile is able turn with this value to correct. I found that this has less effect than track rate.
-Jam resistance (ECM) well I have little knowledge on this, although some missiles can more easily lock the sun itself, or fly through the target aircraft
-CM resistance, as I said the most important - and problematic value. Repeatedly rolled for the multitude of CM packages inside the seeker FOV.
+the hit boxes of target 3D model. If faulty, the warhead will not explode as there is no collision calculated.