Can someone help me with a formula for determining load capacity?

I am building some pull out rifle racks for my gun safe. The best low profile "bottom mount" slides I have found "so far" support a max of 125lbs. So Naturally I want to try and keep the rack as light as possible unless I can find higher capactiy slides that are 1-1/2" tall and bottom mount. I will be installing a top slide as well just to prevent left/right movement. I also want to construct it out of steel since wood absorbs moisture. (I am a former welder/fabricator in my younger years so i prefer to work with steel anyway)

The dimensions of the rack would be 24"L x 8-1/2"W x 48"H and would hold 6 rifles (estimated 60lbs in rifles). This would leave me a max of 65lbs in steel and hardware.

I was thinking of using 1/8 angle iron to build the frame. I am not an engineer, but I don't imagine the sides or top will really add to the load capacity (rather decrease it due to its weight).

So I was wondering how to calculate different angle sizes (1", 1-1/4",1-1/2", etc...all 1/8" thick) load capacity before flexing.

The load would presumably be on the (2) 24"L so it would have 2 pieces of angle 24" long in a |¯ and ¯| formation with an outside measurement of 8-1/2". So there will be a different gap between them depending on angle size. Assuming the center of the 24" is the weakest point, that is the point of interest to me.

Even further, if I could calculate different material thickness (1/16,3/16,etc..) as well, that would be even better.

Thanks for any help you can offer,
Don