Yeah...I shot a M120 powered bearing spring guide out once...knocked over my coffee all over my workbench and smacked into my workshop TV (about 2 feet away). Surprisingly it didn't break the tube...but I thought for sure it did by the sound of the impact.
Another darwin move is putting one together with the spring guide facing your chest if you're up close to the table...not that the spring guide hitting you in the chest hurts...but it'll shoot the half open mechbox away from you across the workbench and scatter all the pieces, definitely ruining your shimming...
I learn from failure....and it seems as though I learn something new everyday