I had several ammunition questions I was hoping someone could shed some light on: 1. Going through "The American Arsenal", American AT Guns such as the 37mm Gun M3, 57mm Gun M1, and the 3" Gun M5, as well as the 75mm Gun 1897A4, all have HE shell, APCBC, and AP Shot ammunition. When the APCBC shells became available, did they essentially replace the AP Shot (which the book often lists as Substitute Standard)? Or did guns continue to be equipped with both AP Shot and APCBC Shells and both continue to be manufactured? 2. U.S. anti-aircraft guns from 37mm on up all have HE shells, APCBC shells, and AP shot. I am assuming that the AP shot and APCBC shells were used solely against armor and that when firing against aircraft the HE shells were used, but I wanted to confirm. Also, it looks like the same HE shells that were used against airplanes were used to fire indirect fire against ground troops (or at least when AA artillery was employed that way)--is that correct? 3. Both the 75mm Field and Pack Howitzers M1A1 are listed as having two types of HE Shell, the M41A1 and the M48. The M48 seems clearly superior having about 40% more explosive and losing only about 150 meters in range. Did the M48 replace the M41A1 or did both continue to be used? If the M41A1 continued to be used, why? Availability, weight?