I've hunted with Triple Se7en in sidelocks using roundball. If you water proof your rifle with a finger cot, you should not have any problems. I sat out there all day in a drizzle and shot a nice one just before dark came and the rifle fired like I had just loaded it.

Since you are shooting a 209 primer you should be more then safe. I have dropped them in water even and they still go off. Your concern should center around moisture going down the bore.

At the end of the day, I agree with you... fire it off or push it out.