[quote=@Ollumhammersong]
over the span of 40,000 years Archaic is a bit relative I suppose. I would hardly call it low damage. They are still supposedly equivalent to .50 caliber. stronger than an autogun or lasgun, just not a bolter. 

 in the end I'll go with what the Dm ruling is. but this weight system is messed up
[/quote]

While it may be an error on the part of the writers, it can also be seen as simply a part of the setting. Armor is massive, guns are big and very much hunks of metal that spit out heavy slugs. War in M41 is fought by giant supersoldiers, horrific monsters, and mechanical titans. Technology is both tremendously advanced and horribly backwards and normal humans are completely outclassed. 

Having a machine gun more like those of WW2 than the lightweight, mobile weapons of the modern day makes sense in a way, considering even the tactics of the Guard is outdated with most regiments using the doctrines of WW1 armies.