yes you can shoot anything you like. The question is would it be accurate.

There are flintlocks out there that shoot 150 grains of powder with sabots if they want. So all that you need to be concerned about is the quality of the rifle. The jaeger with that twist probably shoots conicals. I do not own a jaeger. The jaeger was a true hunting rifle. My understanding is, they lowered the powder charge and also shot roundball out of them. Besides the rate of twist, also keep in mind the type of cut, and depth of the rifling. All of that makes a difference as to what the rifle might shoot well.

RMC Sports sell flintlocks with 1:28 twist barrels that shoot sabots. I have a percussion with a 1"28 twist that shoots sabots beautiful. Also a little fact, lower the powder charge to around 50 grains of powder and a lot of fast twist barrels will shoot roundball also. I shoot roundball out of my inlines sometimes.