[@Sophrus] It should be noted, ogryn are substantially larger than astartes. Ork are generally the size of an astartes when in his power armor. Ogryn, by constrast, well... 
[hider=They're a bit bigger than that.]
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Ogryn average the better part of eight to ten feet tall. It's actually a common misconception that astartes are very large individuals. Most of their bulk is in width, not height. They're taller than the average human, sure, but it's not unheard of for unmodified humans to be just as tall, if not taller, than the boys in blue.