I'm figuring that if it's around 150lb you would be OK. You put 100lb of guns and ammo (that is a lot when you think about it) your at 250lb, if your trailer floors can't handle that, most guys here could not walk in your trailer either. I think a 200lb plus safe would be pushing it. Unfortunately or fortunately you can skimp on the fire protection to save weight. You only need 1 hour protection with a trailer because, God forbid you have a fire, it will burned up quicker compared to a house with more heavier timber to burn and brick walls to make everything inside heat up like an oven. The clay or gunk they use to fireproof safes puts as much weigh into a safe as the steel.