Make sure you specify what world the Guardsmen are from, and what specific chapters the Marines are hailing from.
IA1:
Earthshakers mounted on platforms are sometimes issued with charges 6 and 7, in an attempt to increase this range.
Again, IA3.
...hypersonic passage of each round heated the air so it seemed to fizz and crackle. The speed was such that infantry men stood too close would find the air sucked from their lungs as it passed overhead...
...With void shields flaring against railgun hits...
(After the shields are overloaded by a missile barrage)
...With devastating power two hypersonic shots tore through the thick armour plates in an explosion that showered the surrounding desert in molten shrapnel... (The Warhound Titan was destroyed by these two rounds.)
Some detail on Railgun shots - How fast is the minimum speed to attain temperature to heat the air to 'fizzing' point, or create enough of a pressure difference to suck the air out of men's lungs?
Also proof that the void shields are capable of taking at least more damage than the actual hull and armour plating.
IA5:
...They captured an entrance to a personnel shelter and, after a melta gun had blasted the steel door into molten metal...
Melta gun 'blasts' a bunker's steel door, probably several centimetres thick.
Autogun of of an 'Agripinaa pattern, Type III' specified. Single/Semi/full automatic modes, long 8.25 caliber round (I assume it means 8.25mm looking at the illustration and considering the sheer size of an 8.25 inch round.), full auto firing rate of 650RPM. Muzzle velocity is 820 metres/ps. 20/30 round magazine, anti-recoil measures (weight at the front of the grip to prevent the force raising the barrel as far)..
It's basically an FN FAL, both in the drawing's appearance and in the performance statistics. We can assume a longer accurate range in wind due to the heavier caliber, but with less total range due to bullet drop. Since some Guard regiments use autoguns, this might be useful.
...The leading tank (presumably a Leman Russ, possibly a Chimera. Man-portable Lascannon (From a space marine) erupted into flames as a well aimed lascannon shot tore through its front armour...
Leman Russ's armour plating is 200MM for the turret, 180 superstructure, 150 hull, 100 gun mantlet. Total weight is 60 tonnes, with a height/width/length of 7.08/4.86/4.42 M. At a lowest limit, we also have to consider that the Russ was not destroyed completely (with the crew remaining alive long enough to get out and run around screaming as fire slowly burnt them alive), and may have had 40 battle cannon rounds and 600 heavy bolter rounds.
...the impacts of an assault cannon sent arkos staggering backwards...
Space Marine power armour (unspecified, presumably standard/artificer) is not penetrated by repeated shots from an assault cannon. From IA4, the assault cannon fires a 'fixed cartridge round with a dense metallic core covered in a non metallic sheath with a diamantine tip for armour penetration.' The cartridge is small but accurate at short ranges.
"Doctors keep their scalpels and other instruments handy, for emergencies. Keep your philosophy ready too—ready to understand heaven and earth. In everything you do, even the smallest thing, remember the chain that links them. Nothing earthly succeeds by ignoring heaven, nothing heavenly by ignoring the earth." M.A.A.A