Hence why I said short range. Long range it might be correct, since round musket balls fired from a smooth bore barrel had a tendency to veer off course. But short range (say within 50 yards or so), smooth bore muskets were plenty accurate. If muskets were as inaccurate as in M&M, they never would have replaced bows and crossbows.
M&B just doesn't have the ability to model inaccuracy over distance - if a projectile is comes out of the gun straight, it will travel straight the entire distance. In M&B if you made a gun accurate at 50 yards, you're also making it just as accurate at 500 yards.
I still think the M&M guys took it a bit far though, their muskets are so inaccurate I don't think you could hit a target at 5 yards with any level of success. Due to the extreme inaccuracy the game is purely luck based, you just aim in their general direction and hope for the RNG to score a hit for you. Even point blank you get times where the bullet flys directly down as if your barrel looked like this:
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While playing I had a guy run up on me and another guy with a sabre, both of us saw him coming and turned and shot - the other guy from about 5 feet away, me from RIGHT in his face. Both shots, aimed directly at his chest, missed.
I also had a time where I was slightly behind and to the left of someone, and fired at a guy in front of us. The bullet went sideways and killed my team mate.