Black powder cap and ball revolvers.
I used to shoot black powder cap and ball revolvers, so did my shooting buddy. We would usually have 2-3 that we would take to the range, either Pyrodex or original black powder was used. These were either .36 or .44 caliber, six shot guns.
I prefer outdoors for these, but we were regulars in the indoor ranges too due to the weather being cold in Minnesota in the Winter. I remember cocking and firing my Colt/Remington replicas and just spewing out thick smoke one shot after another like a garden hose, that rotten egg smell. The lanes would look a heavy fog after just one revolver fired, than the other one would go boom, boom, etc. Slow to reload, we were shooting for hours. We saw people leave in short order, than had the place to ourselves gagging on the smoke.
Eventually these indoor ranges outlawed black powder gun usage, but did get "Black powder nights" due to some members wanting to shoot their smoke poles.
The other is when I shoot at my rifle club the .308 cal. AR-15's with the muzzle break next to me actually slap my face from the side blast.