If it is the 1680 with the Cummins you should get about that 3 to 3.2 mph in a 25 foot swath when conditions are good. However if your conditions are like we have being working in the last 3 days expect maybe 2.5 mph. The swath is wet underneath dripping wet and this slows you down alot. Our moisture has been around 16 to as low as 12.5. Good luck
O man. I was thinking it was a bigger machine than my 7721 pull type. Yesterday when it tested 17%, she was able to go 3.25 easy enough. Why would I want a rotary? Give me some reasons guys! So even in good conditions, I'll only get maybe 3 out of her? I'm ill now.
Rotaries shine in good dry warm conditions. Can really put cereals through on good warm day. They are excellent combine when conditions are right but not so great in tuff conditions, that is where conventionals shine. This year our canola was running high 40's. 25ft swath, we were able to easily get over 4mph.
Where are you located? What are your plans with the 7721, we are looking for one to drop straw for baling.
I am curious as to what kind of settings are you using for your 1680? Have you had any luck? We like our rotary because we can get extra productivity during good conditions and also because they are more gentle on sensitive crops. They require more hp but are also generally a more simple design with less drives and moving parts.