The US Army Tests Firefly

The_Chieftain: The argument about angling had occurred to me, but I couldn't think of many practical situations where it would have been a factor. Remember that the M62 APC was the standard projectile fired by the tank destroyers as well as the M4s, and the TDs didn't have any notable problems with anything other than Panther/Tiger II fronts either. One doesn't often read about them bouncing off angled Pz IVs or StuGs.   For the sake of argument: Your theory is fine. Yes, the 50% more penetration could be the difference between penetration and not, in the right circumstances, but it seems that generally said circumstances didn't often present. Take a Pz IV with its 80mm of armor sloped at 10 degrees. Let's say, for the sake of argument, that the PzIV has its hull angled at 30 degrees, and the M4, for some reason, his the front hull. Zaloga gives M62 as penetrating 116mm at 500 yards. If you take the 80mm, angle it at 30, and then angle it at 10, you end up with 93mm (With plenty of exposed 48mm effective of side armour) The M62 has a full inch of overmatch. And the turret it would punch right through without problem. A Tiger's 100mm front hull at 30 degrees was right on the borderline, but not proof either. About the only vehicle against which that extra 50% really would have been decisive was Jagdpanzer IV, not that there were all that many of them.   In any case, the lack of correct ammo is not the fault of the tank. One may as well claim Abrams is useless as a general purpose tank as the US military, in its infinite wisdom, chose not to acquire a HE round until a few years ago. As I point out at the end, the difference between Firefly and M4(76) was that (1) The British thought to bring it, and (2) the British thought to invent hot ammo for it and bring it too. Note that T4 HVAP was produced within a month of someone saying "You know, it might be a good thing to have." It was a planning and allocation failure, not an engineering or design failure which resulted in M4(76)'s situation of being absent and/or under-ammoed. Although I don't understand quite why the British engineers decided to use sabot vice APCR for its hot ammo, the fact remains that they made the specific engineering decision to do it. As a result, the 17pr HVAP (As a concept) is more of a hypothetical figment than M4(76)s capability once someone in charge got their thumb out of their posterior.