Just a handy protip for my youngest brother:

KNOW YOUR VARIANTS!

http://www.designation-systems.net/dusrm/m-9.html
http://www.ausairpower.net/TE-Sidewinder-94.html

Just because the letter is higher, doesn't mean it's better.  The L/M models are the only ones worth fighting with.  The rest are too primitive to be effective; unless it's the X, which is so effective it takes the fun out of everything.

The distinctive fins of the L/M models.

And now you know...