how do i obtain crafting recipes or do i just need 100 survival and repair and they show up automatically ?

also with the reloading benches whats the best ammo to break up to then make 9 mm rounds or 5mm rounds

No, the weapon schematics aren't in New Vegas. Well they are in the game files, but you can't access them without playing on PC.

As for the second part, 9mm rounds require pistol powder and small pistol primer (i think?), 5mm round requires rifle powder and small rifle primer, so see what breakdown recipes result in those ingredents.

All of the crafting recipes already appear when you go to a work bench or reloading bench. It even shows you the needed skills for them. As far as I know you can't throw together weapons like you could in F3. Most of the craftables are cleaned/upgraded versions of weapons you already have.

This page shows all crafting recipes by category. http://fallout.wikia.com/wiki/Fallout:_New_Vegas_crafting

EDIT: Ninja'd

a
aww the rock it launcher thing was soo fun in F3