Greets: I have a question for the more enlightened folk in this section when it comes to bullet setback: Is there one caliber (of those currently referred to as 'service calibers') that would be more susceptible to setback from repeatedly being chambered? Speaking strictly of mass-produced, factory ammo - from the WWB pinking stuff all the way up to the favored defense loadings from Speer, Winchester, Hornady, etc. Let me follow up by saying that I rotate my rounds so that they are not re-chambered any more times them absolutely necessary (after a few rotations, I shoot them up out at the range), but I have noticed that among 9mm/.40/.45ACP and even 10mm, the only ammo that I personally have visibly noticed setback issues with is .40 caliber. This was with Winchester Ranger-T, and the round in question had been chambered exactly 3 times, yet the setback was easily identifiable without even comparing it against the other rounds in the mag. Took it out, lined it up with another round out of the same box, and sure enough... It was set back enough that I put it to the side indefinitely. So the question remains - Are certain calibers more susceptible? I would assume many factors come into play (most notably the contour of the bullet itself), but I was surprised to see it happen on a well-favored defense round like Winchester Ranger-T 165s after only being rotated through 3 times. Granted, this was a sample size of one, which is why I defer to those more knowledgeable than I on this particular subject. Thank you for any insight. Wanna kill these ads? We can help!