I'd bet that's a percussion gun in the sketch. Halfstock, large ramrod pipes, definitely looks 19th century. the puff of smoke at the lock is going forward instead of straight out to the side. The gasses escaping from the vent hole on a flinter are a little roudy as well. My reproduction bess has a 3/32" vent hole. With a stout charge and a 69 round ball the venting gasses go about 7 feet
Edit: the bore on my bess is .740 + so that tells you how easily the gasses vent from the touch hole even when there is plenty of room to go around the .690 ball
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https://imgur.com/a/Bn3sXNI[/img]
