It's completely different than morph animation.
For the most part, the general animating of weapons actual functions and parts, ie trigger, is really a controlled block in the actors kfs. depending on the animation sets you give the weapon in the GECK, will determine what holding animation and reload is played in game. basically all of the animations regarding those things in weapon nifs are bloat data in terms of the game. They can just be deleted. so basically all of those hammer/slide/powercell nodes in the weapon nif have a particularly named block, beginging with "##". those nodes have matching controlled blocks in the kfs. and thats where the animation comes from.
basically what happens in modded weapons is they find a donor animation set. obviously a ak47 and m16 can probably get away with the same reload and firing animations. As you are exporting your weapon, just have the donor in the scene before export. Match pivots of, mag, lever or what every bones are imported with the donor weapon. Export. match the node names in your nif, ie name your magazine object ##mag or whatever. and the game takes care of the animtions from there.
Things get complicated if you want to do a completely different weapon. you can probably get pretty creative with the existing animations if you have too
There are animations you can play inside the nif. they will play constant. and to trigger them on any special conditions starts to get complicated from there. these are the only animations you will need to make, you can pretty much do them completely in nifskope in fairly short time. most of these are basic transform, texture or material controllers. Basically all work the same as in oblivion.
I think it would be possible to add new controlled bolcks to the existing animation sequences. Only really usefull if you do not intend to change the animation in anyway. my example would be to add a controlled blocks to the say 1hd melee, that on equip would play, for example a lightsaber extending. other than that :shrug:
edit: oh, there are no tutorials I know that are any good. everyone(2) I saw was about nif hacking. and thats often messy with f3 nifs. and redundant for the most part.