CM - there is usually a pressure increase associated with shooting hulls of longer length than the chamber. However, the increase in pressure is significantly proportional to the chamber pressure. Low chamber pressures have little pressure increase and higher chamber pressures have more pressure increase. The European (CIP) pressure standards are somewhat lower than USA (SAAMI). Brit guns are proofed/reproofed with CIP loads in mind. Stay away from SAAMI standard loads for older guns. CIP are OK, but lower pressure is better and obtainable. There are good choices available purchase for vintage guns. The use of 2 3/4" hulls really comes into its own for reloading. Most loading manuals list numerous low pressure loads suitable for vintage guns. The key to this issue was a clear understanding of the pressure rise from hulls longer than chamber length; we got it.
