The Warlock group in the Magic World hasn't widely spread the qualities and consciousness of technology.
One of the strongest warlocks in that world—Elf Sage Ada Emin once said a widely circulated quote: My strength comes from possessing knowledge, not sharing it.
Therefore, Lann is not worried that Rita might reverse engineer technology and then spread it out.
That simple and understandable woman would at most fiddle with the firearm with interest for a few days when she first got her hands on it, and then she would return to her luxurious and leisurely life with this weapon that surpasses the era.
Actually, Lann is not worried about the issue of his martial strength being suddenly downgraded a level after firearms are born in the Magic World.
Geralt and Vesemir, old-style demon hunters like them, might face such problems in front of firearms.
But he is different.
Interstellar Warriors were created in the Interstellar Era as Superman Warriors.
