Check out this link:
There are several links on this page dealing with adjusting the B40 trigger, which happens to be a very nice one.
On mine, originally there was no second stage at all which made for a very light but unpredictable let-off. By adjusting the screws, I was able to get a definite second stage increase in resistance, followed by a very crisp break with about 8 oz. of pull. Nearly perfect.