I know, I know, SP 2 is releasing next year, and will probably make this post irrelevant (I can just redo it) but i still would like to share my knowledge.

Briefing

This post is for raw, vanilla, missiles, not custom or modded missiles, but it can be still used.
The XML functions that will be used are:
Turning Performance
maxVelocityAngleAdjustmentRate
maxHeadingAngleAdjustmentRate
maxSpeed
Acceleration
maxForwardThrustForce
Seeker Abilities, and Range.
lockTime
maxTargetingAngle
maxRange
minRange
maxFuelTime
Miscellaneous
ignitionDelay
proximityDetonationRangeMin
proximityDetonationRangeMax
function
name
explosionScale
massScale
dragScale

all the functions will be explained along the way, so lets go!

Turning Performance

So IRL missile turning performance is measured in G, not degrees per second, but in SP1 turning perf. is measured in degrees per second ofcourse, which is neither a blessing nor a curse, but its better than nothing.

maxVelocityAngleAdjustmentRate is basically how much the missile will turn once its max velocity is reached.
maxHeadingAngleAdjustmentRate is the missile AOA, which basically how much the nose will deviate from the heading to turn better.
Now, if we look at a real missile, like the AIM-9Lwhich pulls around 30g's IRL (and can theoretically pull 45g's maximum but will probably break apart)
Now, how are we going to recreate that if the turning performance of the missile ingame is measured in degrees per second?!
Well that's where maxSpeed comes in and... math... :(

IRL, the faster it goes and the more it turns the more G it pulls. And with that, we have an equation to calculate how many degrees per second the missile pulls per G which is: G's * g rad / v or in simpler terms, *G the amount of G the missile is supposed to pull multiplied by g earths gravity (9.80665m/s) multiplied by rad radians per second (57.3), divided by v which is the maximum velocity the missile is supposed to reach.
If we apply this to the AIM-9L which pulls 30g's, and has a max speed of mach 2.5 (around 858m/s or 900m/s for practicalities sake because mach changes alot in flight). And if we apply the formula, we will get: 30 * 9.80665 * 57.3/900 will equal to 18.73 deg/s turn rate, pretty neat right?

maxVelocityAngleAdjustmentRate - 18.73

now what about maxHeadingAngleAdjustmentRate? Well, simply put, its just the AOA the missile pulls + the turn rate. But the problem is, how much AOA does each respective missile pull? Well, that's where War Thunder comes in, our video spons- nah im joking... or am i? Which i am not, using War Thunder as a base, and using Koppany99's and gszabi99's Guided Weaponry Data Spreadsheet, we can see ALL the properties a missile has in War Thunder, now wether this is realistic or not is debatable so always take the data with a grain of salt, add values or remove some, its up to you. Now, if we look at the Flight Characteristics of the AIM-9L and look at the Maximum fin angle of attack: [degrees] stat, we can see it is 22.5 degrees, now we just add it to the turn rate of 18.73, we will get, 41.23, so yay!

maxVelocityAngleAdjustmentRate - 18.73 deg/s
maxHeadingAngleAdjustmentRate - 41.23 deg/s
maxSpeed - 900 m/s

Phew, now that's finally done, we can move on to

Acceleration

which, maxForwardThrustForce is just the newtons exerted by the missile booster. What's unfortunate is that IRL, lots of radar missiles, SAMs have these things called sustainers, which we dont have ingame, so sucks to suck.
Now, we can see that in the spreadsheet, and Engine Properties of the AIM-9L and look at the Force exerted by booster: [N], we can see it says, 10800 Newtons, which is heavily debatable, so, we find other sources, like The AIM-9 Sidewinder missile - Technology, History and Performance which has sources cited, and overall more reliable than war thunder, because well, DCS. Now if we scroll down all the way down to the AIM-9L/M section, we can see that the force exerted by the booster is 1206kg or 11826.82 N which is more realistic.

maxForwardThrustForce - 11826.82

Now that the engine is done we can move on to

Seeker Abilities, and Range.

lockTime which is usually instant irl, BUT we can argue that seeker warm up time can influence "Lock Time", and most IR seekers need 1 sec to warm up and 0.5 for radar missiles. For the AIM-9L it shouldnt be more than 1 second.

lockTime - 0-1 second

maxTargetingAngle is just the seeker FOV, which for the AIM-9L in the spreadsheet is 45 degrees.

lockTime - 0-1 second
maxTargetingAngle - 45

maxRange and minRange are pretty self explanatory, but note, these are the lock ranges, not the actual missile range, missile range is influenced by maxFuelTime. Usually, the minimum lock range of every missile is 30 meters, so 30 meters is good enough. Max range is a lil bit more tricky, which i myself dont even know what to put, but usually, i add the rear aspect lock range and front aspect lock range for IR missiles (3km and 11km for the AIM-9L which would be 7km). For radar missiles, i dont actually know, But if i had to take a guess, i would divide the launch range from the war thunder stat card and use that instead, which is till confusing for somebody who doesnt play war thunder. Now for the function that actually influences max range, which would be maxFuelTime which in other words is just the max guidance time. This is if not the most tricky function to put a constant in, if we put too short of a number, the range will become practically useless form rear aspect, but if the number is too long, the missile would have practically infinite range, depending on the max speed. The best course of action would really only be to experiment, but who wants to do that when a post can tell you what to do? If experimentation is out of the case, you can just multiply the divide max lock range to the max speed we put to get a reasonable output, which in our case for the AIM-9L would be 7000 / 900, or equal to 7.8 seconds. Perfect!

lockTime - 0-1 second
maxTargetingAngle - 45
maxRange - 7000
minRange - 30
maxFuelTime - 7.8

Now for the

Miscellaneous

ignitionDelay, how much time before the booster ignites, which doesnt exist for the AIM-9L or any other IR missiles, it is most prevalent in Radar missiles, which the value would be inbetween 0.2-0.8 secs.
proximityDetonationRangeMin and proximityDetonationRangeMax would be the range the Fuse activates, putting them all at 0 would mean an impact fuze. For the AIM-9L, irl it would have a proxy fuse of between 9-18 meters.

proximityDetonationRangeMin - 9
proximityDetonationRangeMax - 18

function makes it either track Ground, Air, or both targets, the functions to put would be AirToGround, AirToAir or MultiRole, which depending on what base missile you use ingame, youd dearly need them.
name ... its kinda obvious what it is. if you couldnt tell, its the name of the missile.

proximityDetonationRangeMin - 9
proximityDetonationRangeMax - 18
function - AirToAir
name - AIM-9L

explosionScale is well how big, destructive, and juicy (and laggy) an explosion is. Now this is hard to put a number on, because in SP1, its a multiplier, and we dont know what yield it multiplies. But taking the warhead weight of the missile and dividing it by 5, 10 and or 20 may not be a bad idea. (Do note, for the cleaver, it uses the dumb bombs' explosion multiplier, which we do have an explosion yield, which if you are using, please refer to my old post for making realistic bombs). Now the AIM-9L would have a 9.4kg warhead weight, which would be 0.94 if we use our "formula".

proximityDetonationRangeMin - 9
proximityDetonationRangeMax - 18
function - AirToAir
name - AIM-9L
explosionScale - 0.94

massScale would be the multiplier of the missile weight, which for the Interceptor, Guardian and Inferno, would be 85kg, and 1300kg for the Cleaver. Now because the AIM-9L EXACTLY weighs 85kg (what a coincidence!) so we dont need to change the scale at all. dragScale is practically the drag coefficient, which is hard to calculate, so we'll just have to refer to the spreadsheet, which for the AIM-9L would be 3.4

proximityDetonationRangeMin - 9
proximityDetonationRangeMax - 18
function - AirToAir
name - AIM-9L
explosionScale - 0.94
massScale - 1
dragScale - 3.4

THE COMPLETION

Turning Performance
maxVelocityAngleAdjustmentRate - 18.73
maxHeadingAngleAdjustmentRate - 41.23
maxSpeed - 900
maxForwardThrustForce 11826.82
lockTime - 0-1 secs
maxTargetingAngle - 45
maxRange - 7000
minRange - 30
maxFuelTime - 7.8
ignitionDelay - 0
proximityDetonationRangeMin - 9
proximityDetonationRangeMax - 18
function - AirToAir
name - AIM-9L
explosionScale 0.94
massScale -1
dragScale - 3.4

Congratulations! You have just made a realistic missile!

Now, ill try to make a video for more comprehension before January 5, and if i hadnt made one by then, please remind me.

Links used and references:
Guided Weaponry Data Spreadsheet
The AIM-9 Sidewinder missile - Technology, History and Performance
War Thunder
DCS Forums

see ya!