The question was, can 75mm pack howitzer ammunition be fired in the 75mm gun on a Sherman tank as reported to have been done on Tarawa when the tanks ran low of ammunition. I would have initially said this is probably one of many ammunition/gun myths.
This one may well be a 1 percenter. The cartridge cases for both weapons were identical, both had the same head design and a 3.42-inch diameter rim... except. The M5A1 case for the M1A1 pack howitzer was about 3 inches shorter than the M18 cartridge case for the M3 tank gun. The cartridge design was that used on the M1897 "French 75," which was used by the US Army into early WWII. Examining the two rounds pictured in an ordnance manual I see no reason why the howitzer round could not be fired in the tank gun. The cartridge cases and chamber were just about straight, they were not bottle-necked. The howitzer round's rotating band would be about 3 inches inside the tank gun's chamber, but that would not cause a problem. The howitzer round had a lower velocity loading so there would be no over pressure problem. The howitzer round fired from a tank gun might not be as accurate as the intended round, but when shooting at a pillbox from 20-50 yards, which was usually the case on Tarawa, that is not a major concern.
I'll go out on a limb and say it can be done. It makes sense too that the single Sherman company on Tarawa ran low on ammunition. The M4A1 carried 90 rounds and I imagine they went though them pretty fast since there were something like 1,000 pillboxes, bunkers, and dugouts on the island. The Marines had enough trouble getting small arms ammunition ashore, much less heavier stuff and they had low levels of ammunition on hand for several weapons.
23 August 2000
copyright 2000 Wheaton, Illinois
Created 8 October 2000