I again hand over the keyboard to MG Barnes, the head of US Army Ordnance Branch's R&D department in WW2. The previous writing by him, post-war, discussed tank development; this document, however, focused on the guns mounted on those tanks.
Exactly why this memorandum was written is not explained. The date indicates it was after the "tank panic" of Normandy was over, so it may have been a little late for it to have been a 'witch-hunt' to discover why US tanks seemed to be undergunned: One would have expected such a document to have been demanded in July or August were that the case.
Anyway, I present the memorandum again without comment. The OCR didn't seem to like this document very much, so just click on the page images to expand.