Update on my. Z-R5S, took it to the range, had feed issues, took it home stripped it down. Would not pass bolt carrier test, tweaked the back where it was hanging up. It now runs perfect, no more feed issues, up to 1000 rds through it. Disappointed that it didn’t run correct from the beginning, but quite happy now. Tweaking a new gun does not bother me, but Zeniths Q.C should be better on a 2000.00 firearm. I know I could have sent it back and according to others it would have been taken care. I would not hesitate to buy another. It should be noted that I have built two G3 clones that run very well, not sure how I missed the carrier rubbing when I cleaned it prior to the visit to the range, guess I was excited with finally getting a mp5 clone.