+1 on wearing safety glasses.
Another helpful hint is to do the spring/detent assembly with the lower in a gallon size ziplock bag. This should capture the flying parts should you have an oops.
I did this with a cleaner bag. I located myself on the floor of a small bathroom in my house for the first couple I built, figuring they couldn't fly to far and with hard tile floors I could hear it bounce around.
Russellc