how do i make a completely new gun

how do i make a completely new gun, like model and lua scripting

If this includes models it isn’t part of Lua. Models you can use various 3d modeling programs, I prefer 3ds Max.

Here are some tools to use to convert things you make in the 3d modeling program into a source engine usable file:

How to exactly do it I’m not sure, but you can probably google it or ask someone who was an author of a custom gun. Or look around on FPS banana, they have lots of custom skins (Models) there.

On the other hand, with Lua, if you want to make a gun you’d make a SWEP (Link is temporarily down):

Just curious - what program would you recommend that is free?

Theres a 30 day trial of 3ds max, then theres a free version (Forget the name).

I think Milkshape (http://chumbalum.swissquake.ch/) is also good, although I have never used it. The link might be the wrong thing but I’m sure its compatible.