The carrier itself has a max weight of 600lb. I got it from discountramps.com It's built nicely and performed well for the 75 miles I have traveled with it so far. I'm not an expert on the subject, but there are a few things to consider (and I did a LOT of considering).
1 - Tongue weight of your vehicle (the one w/ 4 wheels).
2 - You almost certainly need a Class III hitch with a capacity of 750 lb.
3 - There's a whole mathematical formula to this and I'll give it my best shot, but I"m sure someone on here can shed more light.
There's a rule of thumb where, for ever 12" of space between the throat of the hitch back toward where the bulk of the weight will be carried, you need to subtract 20% of the hitch's capacity. i.e.:
750lb hitch, carrier is 18" back so...
750 x .8 = 600, then 600 x .9 = 540lb
Carrier (100lb) + Savage (350) + oil and gas (40) shouldn't be more than 500 lb.
I hope this all makes sense, but remember to look all this up b/c I'm about 51% sure that it's accurate. haha