recently traded a M3 for a l3 last year. Ran the M3 for 15+ years. Depending on a lot of things with a 16' head average speed between 3 and 4.4 mph. That said it depends on how dry the stalk is, variety of bean, wear and type of rasp bars, set up of concave and engine wear and size. Also how the head feeds the machine will make a big difference. lots of mods will aid in the speed of the machine.
F2_15ft,55bu,4mph,plain ole Hart Carter,10.7-12.8 moisture,long round tooth chaffer (hyper modified)head shatter is all I can find.Concaves-one half-roundn1 followed by 2 rows of rasps n3n5 set at 1_4in clearance with wide space cyl bars.