if you are going to be measuring bullets, a caliper is not the best measurer, a micrometer would be a lot better. I use the Berry's bullets in my 38 special and have not had an issue. Sometimes Jay from Berry's reads this forum and might have a few (More like one or two
) tips. I too am guessing that the case mouth is being expanded too large (Just a guess). As info I have never had a problem with set back with these bullets so never needed a crimp groove/cannelure.