Gun "Smithing"

How could I start to learn about this, I know dissasembly for a lot of guns but I have no clue on what makes it run, how to replace parts etc...

There are all kinds of Tutorials on the web,
Start by doing the research, What are the parts. What part does what.
All GB´s are pretty much the same and work the same way ( Excluding Version 4 boxes ).
Don´t get to wrapped up with Tuning to begin with, grab a few standard Boxes, tear them down, put them back together and test them, if they don´t work find your mistake. Later when you have it down, then move on to the Tuning and Modification side of AS.
It is like starting all over again, What part does what. What are the differences in Main Spring Power ratings, M v %. Do the research on the Different parts, What are they `` Rated ´´ to and what do they actualy hold up to. What is affordable ? What is just a `` Nice to Have ´´ tuning option ? What parts are interchangable ? What parts from what manufacture can be used in what GB or Gun, can they be modified to work ? Can parts be Mixed ? TM with CA With XYZ with Systema. What Metals can be mixed ( Steel Gears / Alu Bushings ? ) What lubricants to use, and where ?

Thats just a small taste of what to look forward too. Right everything down for reference, and don´t be afraid to ASK the question.

Good Luck

Believe me the begining is a B****, but the rewards later are more than worth it.

i have an M4A1 AGM AEG.i already replaced barrel witht MADBULL extended M16 tight.BB still flies up 10 t0 15 yds.i tried adjusting hop up i got the same result.do i have to change hop rubber?does BB gauge needs to changed for 0.23 t0 0.25 higher? thanks

Yea a heavier bb will stop that. Start with .25's

And if you are using a full M16 length barrel, you should replace the M4 cylinder with a non-ported cylinder.

WHOAH posty hijack here! Soap, make your own thread when you have a question, thanks
question was answered though so back to topic.
There are so many threads on this forum about getting started, what you learned, where you learned it, what you need and all that fun stuff. I know I've made a few, and Slob has as well.
Start documenting EVERYTHING you learn on every part, sort of like your own reference guide.