Barrel speeding up, settling in??

[260shooter]

When a barrel speeds up, does it happen gradually or let's say with 80 rounds on the barrel #81 the barrel speeds up to a certain velocity and that's where it stays?

 

[FourT6and2]

When a barrel speeds up, does it happen gradually or let's say with 80 rounds on the barrel #81 the barrel speeds up to a certain velocity and that's where it stays?

Gradually, in my experience.