Lieste

Vark, the difference is that the rounds capable of smashing a Tiger without perforation were unitary 122 or 152mm rounds. As an example of how different these are to modern rounds: 122mm APHE 25kg at 800m/s. This has a short-range terminal KE of 8mJ, and 20,000 kgm/s impulse. 125mm APFSDS BM12 3.66kg at 1800m/s. This has a higher penetration, but a short-range terminal KE of under 6mJ, and impulse of 6,600 kgm/s. 120mm APFSDS M829A3 7.5kg at 1555m/s. This is the largest service APFSDS round in existence - only the experimental 140 and 152mm guns have had larger penetrators. Short range terminal KE is ~9 mJ, but impulse is still only 11,700 kgm/s. While the penetration is undoubtedly very good, the ability to 'crush and shock' is relatively poor still. More of a problem are the large HE that could be fired unfused or with the fuse in delay - these can have a very large impulse indeed. A 152mm howitzer 2A65 fires a 43.6kg shell at 810m/s, giving a short range terminal KE of 14.3mJ and impulse of 35,300 kgm/s - one of these has poor penetration, but the impact could easily unseat turrets, injure the crew and break internal components!

I did consider the increased dwell time, but the blast size of the minor fraction of energy delivered by a small HEAT warhead through the penetration channel do not support a generally lethal direct blast effect when the internal volume of a typical vehicle. The only way to obtain significantly increased behind armour impulse loading would be to greatly augment the delivered blast energy by burning of fuel or ammunition subsequent to perforation of same by (high KE) fragments or the jet. When the blast loading is larger, then the confined space does indeed increase the dwell time in a significant way - now an increased positive phase duration does increase the risk to solid organs. I still consider this effect to be minor though for external impacts compared to the risk to light vehicles from fragment perforations, shock loading via the structure (speed of sound in steel is much higher than in air, and severe damage can be caused to the lower extremities of crew in contact with the floor in IED etc), acceleration/deceleration injuries by bulk movement of structure and vehicle overall, and by tertiary objects (ammo cans/small arms not strapped into racks etc) which can be thrown (at slow speeds) by impact loadings. I consider the movement from floor to roof to be more in consideration of these random unpleasantnesses by mines and IED, rather than to be related to light AT weapons. Incidentally the suppression of fire by Halon extinguishers initially can do nothing except increase current internal pressure. Any suppression and cooling effect can only be related to flame-speed and mixing, and must be a much longer duration effect than those related to blast. They will act by preventing deflagration of fuel/propellant/HE filling of vehicle ammunition, rather than any reduction in incident weapon effects.

As peak overpressure inside a vented and closed chamber is to all intents the same there is no 'survivability' enhancement to the direct effects of the weapon. More likely is the indisputable reasoning that a closed hatch can be jammed if it or the frame are damaged during the impact, either directly or by distortion of the hull. In the case of a fire this would result in potentially wounded crew being unable to evacuate in time. With the hatches open there is reduced risk of being trapped. The riding outside the vehicle was an anti-mine protection measure, as the rigid seats and poor optimisation (pax. facing outwards among other things) would result in a high risk of serious and life threatening lower extremity and neck injuries. Outside there is a higher risk of injury from direct fires, but there is a certain amount of protection afforded by vehicle structures, stowage and improvised armours, and gravity does assist getting off the vehicle quickly if taken under fire.

Without seeing the HT in question it is difficult to give a definite answer, but there are two Half-Tracks that have superficially similar running gear that the Germans are known to have used. The Maultier Ford truck, in both armoured and soft skin versions had four road wheels in Horstman suspension with an idler and sprocket. They also converted two of the captured French Half-Tracks into armoured infantry carriers - the Leichte Schutzenpanzer U304(f), has four small road wheels in two bogies suspended below a heavy bar, and very large idler and sprocket. This one is very like the SdKfz 250. The Mittlere Schutzenpanzerwagen S307(f), has a similar configuration but is much heavier, being an equivalent to the SdKfz 251. This is also known as the Somua MCG/MCL. Although AFAICT neither of the French HT saw action in the east, it is possible that captured equipment and prisoners were used in Europe to make a propaganda film if it dates from later than mid 1944? OTOH, the German Ford HT did see extensive use, and was a fairly standard looking truck when not armoured, or looked boxy and M3-ish in it's armoured ammunition carrier/MRL versions. I am not sure it was ever converted into an armoured APC though. Finally, you shouldn't discount captured Soviet equipment - lend lease trucks were just as popular with the Germans as the original Russian users...