Uhhh... can I ask you to simplify this into terms that I (with the little knowledge of firearms gleaned from CoD and BF3) can understand?
Let me try...
The tolerance is how much variation there is in bullets. Meaning if you cast your own bullets and some of them are differently sized by more than a few thousandths of an inch, they can lose accuracy.
Headspace is where on the round the chamber of the gun is pushed up against. Straight cases usually headspace off the mouth of the cartridge (brass) where the bullet is seated; many shouldered bullets headspace off the shoulder (unless it's a belt fed weapon, which often headspace on the belt.)
Recoil is the force caused by Newton's 3rd law. As the bullet is propelled forward, the motion pushes backward. The amount of inertia depends on how fast the bullet leaves the barrel, how much the bullet weighs (grains), how much the weapon weighs (heavier weapons 'absorb' some of the force of the recoil), and how the bolt works (the 'action'). If the weapon is a bolt action, or a revolver, for instance, all of the recoil is transferred from the weapon to the hand or shoulder holding it (other than what is 'absorbed' by the weapon). In a open-bolt machine gun, however, the bolt which is pushed back by recoil can absorb some of the recoil by the motion of it sliding back in the weapon.
In an AR weapon, there is a 'buffer assembly' which consists of a large spring and a 'buffer', which holds a typically tungsten weight inside it. This assembly is designed to absorb even more of the recoil, which is why an M16 has less recoil than a mouse fart.
Any other questions? I'm not good at breaking things down into formulas like Xavier apparently is. I could probably find formulas and more accurate terms if I looked online, Wikipedia and so forth, but I'm just going off memory here.