I don't think you want to make summer sausage from breakfast sausage. They are two different seasonings.
Eat the breakfast sausage as is.
Make summer sausage from ground (what you have) and mix in pork or beef.
I just made a batch of summer sausage with a Cabelas mix. It came with seasonings and casings for 25 pounds. I used bear and beef. It really turned out great.
I did it in the ancient Big Chief for 3 pans and then finished in the oven. Had to clean the oven after that.
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The Cabelas package said use pork but I went with beef and no complaints. I'd link a pic of the box from Cabelas but couldn't find the one I used on line. It's hard to miss in the store (Tulalip) as they had a ton of it.