Let's assume the 'auto cannon" in the "Nightbringer" example is 30mm. For shits and giggles, we'll assume an ETC gun like performance (something on the order of 2 km/s) and a 300 gram DU shell. At the speed and velocity mentioned, each shell will carry something like 600 kj of KE and 600 kg*m/s of momentum. Your average Space Marine might get knocked around a bit, but ususally masses half a ton or so (Deathwathc RPG) so we're not to far off in terms of knocking him about (although 600 kg*m/s is, in my opinion, pushing it). Something of a WW2 era armour piercing anti tank round? 800-1000 m/s and say 7-10 kg shell (Ex: the HVAP ammunition) would pack 7000-8000 kg*m/s worth of momentum and 3-4 MJ of energy or so (at least) nevermind something more APDS or better. That sort of lethality would be knocking Marines off their feet if they were taking such impacts - have we ever seen this performance form heavy bolters or autocannon? I haven't seen it.
Oh, and nightbringer? Let's look at the instance:
Note the bolded part - it does not sound much as if this guy is getting rocked around violently by the levle of momentum I'm tlaking about - he seems fairly immobile in fact, which indicates my earlier assessment was generous. But regardless it is quite obvious he is taking nothing like a MJ range autocannon hit - such would need more of a half a kilo to a kilo shell at the aforementioned 2 kps and would packthousands of kg*m/s - enough to be severely knocking the marine around - something we have NEVER to my knowledge seen, much less the KE/momentum of something ACTUALLY of a reliable anti-tank grade.Nightbringer wrote: Heavy autocannon fire sprayed the roof of the building, churning up its pebbled
surface and shredding human flesh. The men who had been awaiting rescue in the
flyers were the first to die, ripped apart in seconds by the heavy calibre, armour
piercing shells.
..
Learchus sprinted forward, diving to the ground to gather the girl in his arms and
rolling on top of her as the ornithopters shells ripped towards her. He supported his
weight on his elbows so as not to crush the girl and felt the powerful impacts hammer
into his back plate. He offered a short prayer of thanks to his armour for standing
firm against the traitorous fire.
Insofar as specific Space Marine resistances go in other sources, the armor has been penetrated by bolt guns (Common throughout the Horus Heresy novels or pretty much any novel or source where Marine fights marine) It has been penetrated by heavy bolters (Let the galaxy Burn short story featuring dark angels has a heavy bolter that repeatedly penetrates Dark Angel armour and ruthlessly kills those wearing it.) Iron Hands has a Iron Hands Devastator using a krak missile (anti tank warhead) to not just penetrate Space Marine armor, but blow the fucking marine APART.
So again rather than this inanely retarded insistance that "FUTURE AUTOMATICALLY MEANS BETTER!" and other such retarded resistances, why don't you actually provide the evidence (quotes, numbers etc.) demonstrating a fucking Space Marine can stand up to a fucking anti-tank weapon - the point which is relevant to the fucking discussion. If I have to ask again I'm going straight to Edi on this.