Poor Shotgun. Never did it shine.
Dunwich was released, bringing with it Lightning Gun, a king who reigned for two years. While the shotgun might do 10 damage in 2 shots, this was still an unsure bet, netting all 5 damage was a struggle compared to the nonchalant unaided ease a Lightning Gun did 3. Securing hits was just that much better.
M1918 BAR made its appearance in the latter half of Forgotten age, challenging the king and pissing all over Shotgun as a weapon that could with tremendous reliability do the damage shotgun was supposed to be the best at: lots of damage in just 1 or 2 shots.
And now finally, Flamethrower has taken the seat of the king, outpacing all three guns with hilarious efficiency at the measly cost of not being able to wear a Bandolier.
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So, where does my dour opinion of Shotgun come from?
Here: The hypothetical target is a 4-fight 4-hp foe, you're a Roland Banks, the classic , and you're toting an Overpower. With the card committed and a shot from the gun, you shoot with +9 to hit, against the 4 fight foe you're at an advantage of +5.
Now, you might draw something like a -2, skulls and cultists often have this penalty and the standard deck often has 2 of these, so a very common number, the net result is that you beat the target by 3, meaning that the thing you just shot with half your ammo from a 4xp card and a skill is still alive, the token was far from terrible and still the monster is alive and kicking. Add a Beat Cop to that equation and you're back at square 1 if you drew a -3 or a special token that at the moment has a larger penalty (as is usually the case with harder, latter half of campaign, scenarios).
I'm no fan of power creep or OP weapons like the Flamethrower, but the Shotgun just doesn't perform as advertised, it never has.