Haven't seen those things in years..seem to have evaporated..last to sell them was Archer's.
A good number of posts/tests about 10 years back.
Really simple "U" design(with thicker "legs" than the curve)..rebonding hammer would jam the thicker legs against the pin slot..basically a friction brake.
It worked reasonably well with factory rough pin slots....didn't work with well polished pin slot....and it tended to self-polish with use.
Had the elegance of simplicity.
Yes, that is exactly what I had, but after years of flawless operation, it finally failed. It just basically wore thru where it contacted the cocking slot sides, and ceased to function. I'd love to find another one, or for that matter, any other solution to hammer bounce in a QB.
I have Steve's free-flight hammer devices in 3 of my Snowpeak/Diana CO2 guns, and they work very well. I just need to do something with my QB.