There are two distinctly separate problems in FL resizing: Headspace (base to shoulder dimension) and case diameter(s). With excessively "long" cases the case will enter and extract relatively easily, but the bolt may not fully rotate to the locked position. Correcting this is a matter of die adjustment, shellholder selection and in unusual situations, modifying one or both. The problem of case diameters is potentially more difficult. Excessive case diameters are usually at or near the web. Attempting to chamber oversize (diameter) cases can result in the case firmly stuck in the chamber, far short of allowing the bolt to rotate fully. If it is a live round, you have a potentially dangerous situation. Repeated attempts to force the cartridge into the chamber just make the situation worse and even more dangerous. Gauging cases is tricky. An appropriate barrel (or chamber section) is an excellent "gauge" for checking diameters. The case should drop in easily and come out with just gravity or a fingernail. This will not determine if headspace problems exist. The drop in headspace gauges have limited value. They do not check diameters and only provide a crude headspace check. A micrometer type such as the RCBS or your rifle's chamber is a better gauge. The OPs problem is most likely with case diameters. Springback is probably less likely than an initial failure to get adequate size reduction or a die that simply doesn't size the case all the way down. Often forcing the case into the die twice during the FL sizing helps. Proper case lube and die adjustment are also factors. I have often mentioned that dies vary.....and they do, year to year, between manufacturers, and even day to day. I have a standard .308win RCBS FL die that sizes smaller than a RCBS SB die for example. Good Shooting. ... using a 30-06 die on 7.62mm brass excessively reduces the .308 case diameters throughout the entire case length while not affecting the web diameter much, if at all. The entire .308 case will be so reduced that it will chamber even if the web is still somewhat large. It will then expand greatly to fit the .308 chamber when fired. It is a solution that will work for the wrong reasons. Any ...one with a digital caliper can can easily confirm this.