Editing Warhammer 40,000/9th Edition Tactics (section)

====Inflicting Damage====
When a model fails its saving throw it takes an amount of damage depending on the Damage characteristic of the weapon used. The model suffers that many wounds and any excess wounds are lost if not mortal; excess mortal wounds are allocated using the standard rules for allocating wounds, but since mortal wounds skip the saving throw step, you proceed immediately back to this step. If it is suffering both non-mortal and mortal wounds from the same attack, resolve non-mortal wounds first.

Feel No Pain "FNP" style abilities allow models to ignore some of the damage they take on by rolling a die and beating a number; these rules are exclusive, meaning you have to choose exactly one to use.  Some of these rules may specify that they work only on non-mortal wounds or only on mortal wounds, or in different phases, or what have you, but they generally all work the same.  This means that an FNP "save" is theoretically like an invulnerable save, but worse, as invulnerable saves are not negatively impacted by trying to resist greater damage values.  In practice, invulnerable saves are ''much'' easier to get.

Roll a die for each point of damage the model would suffer. On a roll of X or more (typically 6), ignore it.
*Sometimes, the roll is a 5+.
*A 6+++ FNP ''generally'' increases the average number of wounds you need to deal to a model to kill it by 6/5 or 20%. The chance that it will completely nullify an unsaved wound is 1/46656‬ for 6 damage, 1/7776 for 5 damage, 1/1296 for 4 damage, 1/216 for 3 damage, 1/36 for 2 damage, and 1/6 for 1 damage.
**This gets messy, quickly, because of how excess damage is wasted: while you will usually need 6 damage to kill a W5 model with a 6+++ FNP, it will actually suffer some damage between 0 and 5, as both 5 and 6 damage getting through kill it.  This means a W5 model suffering 6 damage actually takes about 4.67 on average (and has a 73.68% chance of dying outright), while a W1 model actually takes very nearly but not quite 1 damage, with the same chance (nearly 1, which is nearly 100%) of dying outright.  Meanwhile, a W6 model without an FNP takes 6 damage, with a 100% chance of dying outright (in this case, making it 'less'' durable than the W1/6+++ model).  Generally speaking, W is better for resisting lower damage (W6 can't die to D5, while W5 can, regardless of FNP), while FNP is better for resisting greater damage, relative to some starting W.  
*A 5+++ FNP increases the average number of wounds you need to deal to a model to kill it by 6/4 or 50%. The chance that it will completely nullify an unsaved wound is 1/729 for 6 damage, 1/243 for 5 damage, 1/81 for 4 damage, 1/27 for 3 damage, 1/9 for 2 damage, and 1/3 for 1 damage.

This means you can ''usually'' roll the dice for all of the non-mortal wounds a model is suffering at once, as order does not matter - enough failures to remove the model's remaining wounds kill the model, and the excess is wasted - but remember that special rules can apply (such as a model that only gains an FNP after it suffers some damage, or a weapon that lets non-mortal wounds spill over to other unit members).  You can't do this for mortal wounds in a unit with mixed FnPs, as each time a model dies, the unit's controller can choose a new model to start suffering remaining mortal wounds.