Bolt rounds

 The mere shockwave of a passing Bolter round causes internal bleeding in the brain and organs of those on a 1 meter radius near it:

"Barsabbas reacted as he was drilled, pressuring them witha wide spread of automatic fire. The sudden volley of crackling bolt shells cut out in a semicircle. Rounds so heavy that even their passing shockwave haemorrhaged the brains and organs of any target in a one-metre radius." - Blood Gorgons



Storm Bolter rounds can penetrate through 8 inches of plasteel as if it were tissue paper:

"The storm bolter, the Space Marine's standard firearm, fires small, high velocity bolts with explosive tips, capable of blasting through eight inches of plasteel as though it were tissue paper." - Space Hulk



Storm Bolter rounds can also penetrate through tanks:

"Alvez, dressed for battle in a massive suit of Tactical Dreadnought Armour – better known among the Astartes as Terminator armour – fingered the trigger of his twin-barrelled storm-bolter. The weapon was large, much larger than a standard bolter, and fitted with a heavy box magazine. They made a nasty mess of organic targets and its oversized bolts could rip through the side of a tank if they had to." - Rynn's World



"The bolt pistols thundered again. Each round found its mark, and fifty more bodies were reduced to bloody fragments. The rest of the mob staggered on, their outstretched hands little more than a metre away. At Zahariel's command, the squad took one last step back and fired five more rounds into the press. Firing bolts locked back on empty magazines as fifty more bodies erupted into gory mist. The mob had been cut in half in the span of twenty seconds, but the remainder pressed their advance." - Fallen Angels