Have you tried any of these?
https://history.saab.com/en/archive/
I have only found images of the Bofors in the archive. There don't appear to be any contact details, perhaps Saab can help:-
https://saab.com/
In 1999 the company Bofors Test Center, now owned by Saab Dynamics, BAE Systems and Eurenco Bofors, was formed:-
https://www.testcenter.se/about-us/history/
Weapon Systems Sweden (Bofors) is a part of BAE Systems’ Weapon Systems:-
https://www.baesystems.com/en/our-companies/our-businesses/platforms-and-services/locations/sweden
Have you taken the springs and/or explained what you require to a spring maker?.
If, you search "spring calculator" most of the sites that come have a Spring Rate Formula.