The J lock device doesn't do anything to cause bad accuracy or to slow lock time. It just gets blamed for this crap by people that can't shoot for crap in the first place.

All the J lock is is a groove cut in the rear of the firing pin so the little lock can be rotated and lock the firing pin in place.

Other than just looking bad it does nothing good or bad for the gun. Actually if it does anything to lock time it would speed it up slightly since there is an aditional cut in the firing pin and it is slightly lighter.