I see I can choose a Mercenary Licence, Explosive Collar, or Infantryman's Uplifting Primer. I find what the explosive colalr does but can't find the mercenary license or the primer anywhere in the books or errata do they have an in game funtion other then fluff?

Just fluff, pretty much.

What MILLANDSON said, though the Primer gets some love in the Inquisitor's Handbook.

You can consider the mercenary license a license to carry around heavy ordnance. In a setting where almost everyone sane and able owns a gun you can run around with a machine gun without arousing suspicion.

The Primer is great if you have the physical version from Black Library. Nothing beats a good quote or prayer read directly from the Primer during a fight.

But all those 3 choices are fluff based, showing whether you are a true guardsman, a mercenary or an ex-con.

True, these mostly serve a background function. Still, all three have some mechanical use as well - i.e. the primer has some information on military hardware, xenos, and other things that a starting character has no other source to know. Mind you, this information needn't be entirely correct and unbiased - it's the Infantryman's Uplifting Primer, not the Infantryman's Factologically Correct Encyclopaedia of All Things Knowable and Unknowable.

The_Shaman said:

While that might be true for such sections as Survival Techniques, Specific Items of Arms and Equipment, Principles of Battlefield Physic Aid, and Rules and Regulations; most of the information presented in the primer is dead on accurate and unbiased information that could save a Guardsmen's life. Like that large box on pg 54 which advises the Guardsman to "Keep this space clear. Do not deface. On pain of Death." Good strait forwards unbiased information on how not to die. This book also presents all the information anyone could ever need to know about the enemies of man!

"An ork can seem an alarming prospect when first encountered. They stand teller than a man, with hunched, broad shoulders and long arms. They may seem to be heavily muscled, but the fact is their muscle tissue is not as dense as a human`s. In actuality they are considerably weaker than the average man, despite what their appearance suggests. Their skin is thick and coarse and ranges in hue from green to almost black. Portions of their body are covered in stiff, black hair. Their brow is heavy (denoting their lack of intellect) and their little, almost useless eyes have a red cast to them. They have greet tusks which jut from their mouths, but they are not sharp and a firm tug will pull them out by the root.

When confronting orks in combat remember their weaknesses and consider the facts; they are but animals, and they have no place in our galaxy where they prey only on the weak and helpless. After they have seen you with a loaded lasgun and a smile on your face, you can shoot them in the back as they run away!"

FACTUAL!

"Tyranid weapons are formed out of living tissue; they often fall apart"

ACCURATE!

"The form of the tyranid is manifold, Some stand far taller than a man, and are slow and cumbersome movers. Other, faster ones are the size of dogs, but they wander harmlessly at the feet of their larger brethren, often tripping them. Most are armed in the main with claws, spikes, flesh hooks and bony extrusion that form natural extensions of their limbs.

Their strength, such as it is, is in close combat fighting. But even in that case a tempered blade thrust firmly in between their armour plates will incapacitate the attacker, and convince its brethren to back off. To avoid getting your uniform coveted in alien ichor it is best to dispatch them from a distance. Indeed, massed fire from such high technology as a lasgun will confound and confuse a tyranid swarm, allowing you to pick them off at will."

GOOD ADVICE!

"Disposing of the Alien

You have by your side the tool of cleansing. Your standard issue lasgun is your instrument to met out the Emperor's Judgement upon the unclean xenos. The alien is weak, and the white-hot heat of a las-round will be enough to end their miserable lives. Treat them as you would a blood-leech clinging onto your belly: a parasitical irritant, a thief of essence, an taker of life to be purged! Bunt! Cut out! Ground underfoot Destroyed! Annihilated with a prayer on your lips!"

UNBIASED!

Arag said:

Or to see the litany of the void actually being used during the case of a hull breach.