WHY DIDN'T THEY JUST SLAP MUZZLE BRAKE ON THE M-4 SHERMAN'S 76-MM GUN TO TAME MUZZLE BLAST?We're talking about the US military in World War II and they did not seem to be thinking clearly at the time. The issue was that US tankers manning 75-mm gun armed Shermans were reluctant to accept the 76-mm M-1 wholesale (they wanted limited numbers only) for several reasons, one being excess muzzle blast obscuring the sight of the gunner and captain in dusty conditions, making it harder to note if a hit was made and if not then how high and wide the shot went.To a layman the obvious answer is Just fit a muzzle brake on the danged gun! Ironically, it isn't as easy as that: muzzle brakes are heavy. The elevation system and other parts of the gun has to be set up to handle a heavy weight on the very end of the barrel. For example, the first 600 of the 90-mm gun armed M-36 tank destroyers issued did not have one and as far as the military was concerned they never would. They weren't set up to accept one and there wasnt' time to convert them. (They were pressed for time and trying to get them into service; and the 90-mm had less of a muzzle-blast issue than its smaller kin).The issue with the 76-mm was that once the need became apparent, the actual devices were not produced fast enough. Thus, many tanks went to war with a cap covering the threads on the end of the barrel where one would be attached if it was ever provided. The initial tanks didn't even have threads on the end of the barrel to screw one onto.Of course, the powers that be could have developed the gun with a muzzle brake in the first place. Despite testing and plenty of time to work it out, the Ordnance Department didn't foresee a need for one. Perhaps they had lulled by the experiences of the M-10 tank destroyer units who mounted a 3-inch gun without a muzzle brake. It created excess blast and smoke, but the M-10 crews didn't complain. Maybe they didn't know better; and certainly they actually didn't get into a lot of fighting. The M-10 had been designed and the crews trained to counter the feared mass of panzers the Germans would throw at the USA. Which didn't happen until December 1944. While ground forces did encounter German tanks, they often were not that much an issue during 1943 and 1944. They tanks often took care of them first. There were long spans of time when US ground forces met very few German armored fighting vehicles.And thus the M-10 crews spent a lot of time in their intended secondary role as mobile artillery. And occasional jaunts supporting infantry. Front light fighting was not something they did a lot of, so why were they to complain about muzzle blast and HE shells?Whatever the case: the Ordnance Department dropped the ball and it took a little while before 76-mm guns with muzzle brakes arrived.They not only added a muzzle brake but also changed to a long primer ammunition (which no one has explained so far, but perhaps it results in better ignition of the propellent ans less smoke).