In addition, to his Mechanicus "brethren", a Master of the Forge is often seen as the worst kind of Heretek, loyal to the Quest for Knowledge in name only, a warrior who does not hesitate to bend and adapt a Machine Spirit to his needs instead of carefully entreating and revering it as the Cult Mechanicus prescribes. While often excessive, there is a core of truth in the Mechanicus' accusations, for a Master of the Forge is first and formost a Space Marine, a warrior of the Emperor tasked with ensuring that the Astartes in his care always have the means to wage war at their disposal. Few Masters of the Forge hesitate to modify or even completely overhaul a weapon or vehicle to better fit their Chapter's need, to the dismay and outrage of the more conservative Tech-Priests.
New patterns of existing vehicles developed by a Master of the Forge are often grudgingly accepted and blessed by the Mechanicum only after painstakingly slow and lengthy examinations, when they are accepted at all. Some Masters of the Forge, tired of waiting for an unrequired approval from dogmatic non-combatants, have simply spread the specifications of their craft to their fellows of other Chapters, bypassing the Mechanicus entirely, which has only served to stress and antagonize the relationship between Astartes and Mechanicus further.
I don't see it as stretching myself, but then I see it as more of something one can learn overtime, adn even the Tech Priests at times refuse to share any knowledge gained with another, lest they feel they taint it or plan to use it for their own usage.
If this had been an Aspirant or new Tech-Marine I could vastly see it as stretching it, but a Forgemaster? Not so much.
Regardless, I've certainly been enjoying the new version of Chapter Master, so much has improved since I played it last!