Question regarding the crafting rules.

The book says that Tech-Use items are "fiendishly complex, or their designs a closely guarded secret, and are only available to characters with the right knowledge" and the foot note on the crafting table says "characters cannot create items they do not have access to designs for."

So, the question is how would a Tech Priest gain access to designs? I cant find any rules or guidance in the book.

My first idea is to let the Tech Priest start with designs related to the gear he starts with. For example my group's Tech Priest is starting with a Hand Cannon so I am thinking he would know the designs for Solid Projectile Weapons of Scarce or lower availability.

Am I way off the mark here?

STC designs are a big deal and not something a Tech-Priest "just" gains access to by visiting a library or universitat. Building a new design or even heavily modifying an existing design is considered illegal according to listed weapons' fluff. Custom weapon designs are important to me as well, so I explored ways I could have create weapons without provoking the Tech-Priests. The compromise I reached was thus:

1. Use one or more of the following Skills to analyze a weapon:
   • Relevant Common, Forbidden, or Scholastic Lores (such as [Adeptus Mechanicus] or [Tech])
   • Logic
   • Tech-Use
   • Trade (Armourer)
2. Beaming the results to a dataslate or similar medium, tinker with the design in virtual space.
3. Do not actually build the resulting weapon.
4. Send the design to a Tech-Priest in power where he may publish the design as his own but possibly give you credit.

For a new Acolyte, this system is fairly reasonable. Going straight to production without political backing is going to have some heavy reprecussions. Surrendering original tech and documentation immediately upon questioning is another option. That way, a Tech-Priest can have his creations until someone calls him out on it, hopefully without accusing him of tech-heresy. At higher Influence, individuals may be able call their designs their own without inviting retaliation.

Thanks for the advice. You do make a good point that some random Magos would not have access to the STC template for anything. He would likely have to own his own Forge World and maybe then.

I do like the steps you outlined. It also lets me as GM introduce complications in his design if I do the Tech-Use rolls in secret. He could analyze the weapon and think he has a good enough understanding, then build a copy and "woops you just made a bomb that blows up in your hand when you pull the trigger".

If the Tech-Priest is just wanting to copy an already existing weapon, would he really have to get permission from other Magos?

From a narrative standpoint, I would say yes to requiring permission every time until the Tech-Priest moves up in the world. Even then, it wouldn't hurt to alert other Tech-Priests that "hey, I'm trying something new over here but it's not like I'm doing so maliciously." Depending on how closely you want to follow the setting (stagnation and uniformity), my measures above are appropriate. But, understandably, that is horribly stifling and discourages people from using any sort of Crafting Skill. A more lax or generous GM will waive the narrative reprecussions of hitting the market with ne'er-before-seen tech, but other GMs would want to play the grimdark setting for what it is.