I thought that a lasgun shot was supposed to hit considerably harder than a modern rifle. Like, "blows limbs off of unarmored humans". As such I assumed they were on par with autoguns in that they're more powerful, but fire slower.
Am I wrong about how powerful lasguns are? Do autoguns actually fire the equivalent of .50 cal? Are lasguns actually more powerful than autoguns overall?
In the RPGs the basic lasgun does 1d10+3, an autogun does 1d10+3 as well, the later editions added the ability to power up your las weapons with +1/2 damage and +1/2 penetration at the cost of 2x and 4x ammo consumption. There are also hotshot lascells that make a normal las weapon into a weaker hotshot lasgun but with way less shots and higher price.
The lasguns main advantage is how easy it is to get more ammo. You can plug a battery into any standard power source and get a full clip in a few hours, an autogun needs purchased ammo so you can't get it until you go shopping which eventually laves you with s glorified club0. The autogun also has a smaller clip of 30 so you need to reload more often, even if it's better at mowing down multiple weak enemies at once, which can be deadly in a firefight.
Both weapons are fine for fighting normal human grade enemies, like cultists or normal guardsmen, but become basically useless 1v1 against the more dangerous or well equipped enemies. Special ammo types extend the usefulness of the basic weapons, but there's basically no circumstance in which a basic lasgun or autogun can stop a marine without scoring the system's critical hit equivalent or a massive numbers advantage.
It's important to remember the novels that describe lasguns as blowing off limbs or punching right through power armour are generally older ones where the general power of weapons wasn't very concrete. More recent lasgun fluff desribes them either blowing little craters in flesh (generally against big monstery types) or boring a hole into the body that then causes death from the swelling of internal organs as a result of heat and trauma (from a medic's field injury guide from one of the big rulebooks.) Some stories just treat them like bullet based firearms.