Long Stuff not left for space purposes.
Wait till my summary.
Source on M107 shells:
http://www.globalsecurity.org/military/systems/ground/m107-175.htm
Source for Chobham armour:
http://www.economicexpert.com/a/Chobham:armour.htm
About the stuff written about fire destroying and Galleom....we conlcluded that G.B's fire is not hot enough to melt a heavily reiforced metal. If it was plasma or at least white fire, then yeah, but G.B's fire is red ( the least hot type of fire there is) and that won't do anything against chobham armour or simply armored vehicle armour.
About the fire destroying the shells, just to see how much sense that makes, try to imagine a guy destroying an artillery shell mid-flight with a flamethrower. Doesn't make much sense unles you are giving G.B his Mario Sunshine fire breath.
And about fire instantly destroying galleom because of fuel and explosives....take into consideration that artillery vehicles have chambers especially made to stop the explosion from destroying the rest of the vehicle if they explode. And the fuel is always inside a heavily armored chamber of an armored vehicle.
Lastly....let's not get TOO technical here. Let's forget that Galleom's feet would not support his weight because then we would just say that G.B would be as slow as your average giant turtle. Or worse, that he would be crushed under his own weight because his shape is not made to support that much weight.
Please people, let's not be TOO realistic by including physics into the mix. It ruins the fun.
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New points.
Galleom aproximate MAX range when shooting those shells: 40.0 Km.
Galleom can have multiple types of artillery, the M107 was just an example of the type of ammo he could have.
125 mm smoothbore anti tank rounds.
Panzergranate 39 armor piercing shells.
And if he is a futuristic robot then it would make sense that he has the technology to accurately lock-on targets from very far away because, well, we already have that technology
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[We never talked about his vehicle form.
Vehicle form>Giga's shell. He basicaly eliminates any weak-points he may have, he can move, is faster than Giga, can shoot missiles from afar and get away, is comletely covered by it's armour and can ram pretty hard.
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There is also the pain and tiredness factor.
Galleom can act at full power as long as he has fuel. Giga will gradually get tired, and even more if he has to carry such a heavy shell.
Galleom does not feel pain, so he can MK walk his way thru Gigas fire and attacks without feeling a thing. Giga still feels pain and he will still feel pain if he gets hit in his shell, as long as the blow is strong enough.
And lastly, if Galleom gets crippled or gets one of his limbs severed, he will still be able to fight and shoot projectiles, without pain interfering with his mission. Giga gets crippled=Giga falls on his feet due to the pain.
I am pretty sure Galleom has this one.