If you ever measure carrier velocity changing the spring does even less than changing the buffer to rearward speed. All it does is decrease the rearward dwell time and give the magazine less time to do it’s thing.

Sprinco also has had a note for at least a decade on what spring to use, especially with ‘newer Colt 6920s’. News flash: Colt 6920s have only ever had one gas port size.