A question for you WW2 history buffs.
 

Why was the MG42 allowed to fire so fast?

I understand that there was a psychological aspect to it.

But as a practical mater, I would think, the need to change out barrels and the rate it went through ammo would hinder it's usefulness.

Wow, that's an obscure one. But, my guesses:

1) Most infantry are trained to only fire off short bursts anyway. The whole full auto, unload on people idea was never really a thing.

2) Even with the swapping out of barrels, my guess was the overall cost of parts and speed to manufacture still kept it cheap. Germany's biggest problems were always resources & production capacity - anything effective that was cheap to produce woulda been gold.

It doubled at times as an anti-aircraft weapon, where the high rate of fire capability was useful. For use against ground targets there were strict orders to keep the weapon limited to short bursts.

From what I've read it was more reliable than the MG34 that it replaced.