This is an inherent property of closed source proprietary weapons. Which is why gun owners like stuff like the gen3 glock and ar-15 as everyone knows how to make the parts and the open source blueprints are put into manufacture by a gazillion companies to the point PSA shitwagon can compete with a Colt and interchange most the parts.
Maybe Europe should open source a fighter jet and let the world compete on how they'll manufacture it.
As an observation, when the US originally licensed out the AR-15 to other countries they often also had to license aluminum foundry tech at the same time. We take it for granted now because that tech is old.
The ability to scale advanced or exotic materials science at will was a cornerstone of why US weaponry is difficult to copy. People always underestimate this aspect but it is a major reason why manufacturing of state-of-the-art hardware is not fungible.
Europe's weaponry is already somewhat "open source". Many big things like aircraft and missile systems are designed and built with pan-European consortia. As a result, every country knows how to build these things.
Heck, even Italian Agusta sold some of their platforms to a NATO ally with build/iterate/export permissions...
Look up the F-35 sometime. For Germany's F-35 fleet, Rheinmetall was going to build the fuselages and do final assembly in Germany. Splitting up the work like this isn't unique to products from Panavia or similar EU-only consortia.
Maybe Europe should open source a fighter jet and let the world compete on how they'll manufacture it.