ExistingThing has a very cheap solution to the Walter G22 (.22lr bullpup rifle) trigger problem.

The Walther G22 has a terrible trigger, lots of take up, and a very mushy break. I saw it as an opportunity to practice my trigger control, and got pretty good with it. After a recent trip to the range I took it apart for cleaning, and decided to spend a bit trying to figure out a cheap, reliable, effective way to shorten the trigger pull. Previous attempts had been fruitless, but this time I actually figured something out.

More here.