My Uncle would have agreed with you on the 6 Pdr. He was a Tankie Gunner in the first N Africa battles and they were equipped with tanks with the ubiquitous 6 Pdrs. He was much of the opinion that, apart from the tin can they were sitting in, a pea-shooter would have been just as effective against German and Italian armour. Later he got promoted, as someone discovered he was well qualified, and said the replacement Shermans and [i think] Churchills were far more able to disable the opposition, rather than just rattle their ear drums.
As an aside, he did comment that the Italians had a reputation for having tanks with a reverse gearing faster than forward - his one comment on that, was that he personally found no such evidence!