I'm going to call tomorrow and ask, but I wanted to see if anyone on here knew. The AMHS website states

"Small quantities of ammunition (Not to exceed 100 kg (220.5 lbs.) for handguns, rifles and shotguns, may be transported by passengers provided they are securely packaged and carried separately from any firearm that is being transported. No black powder in any quantity is allowed. Customers should check with local terminal staff for the AMHS policy on transporting firearms."

Is the 100kg per person, or per vehicle? If I have four people in my RV, and buy four tickets + the RV transport fee, does that mean I can have 400kg of ammo in the RV?

Yes, better to call.  Ammo limit was like 65# when I did the ferry.  I had to call two places to find out how much smokeless powder they'd let me take...neither had a good answer and kept telling me to call the other.  One asked how much I wanted to take and I gave them an answer and they said no problem.

Small containers 1#? of propane (case) were not a problem either, but an extra 20# tank I had to store in the ship's paint locker.

Enjoy the trip!