I just realized I performed 1 other item before this last BTF test. Round count was at 200 and I detail cleaned the grooves in the slide where the slide rails travel. I didn't care if I removed any copper lube, I just wanted them spotless. Needless to say, a lot of black came off on the cleaning patch. I wonder if it was buildup from the new top finish Glock is using on the slides. Could that be slowing the slides down enough for BTF? Wanna kill these ads? We can help!