Submersble pump hp size and water well depth

Is a 1/2 hp 5gpm goulds pump adequate for a 300' well? I had a company install one, however, I get very little pressure delivery. This is with a new 30/50 pressure switch and new prepressureized tank. I looked on charts and a 1/2 hp pump does not even register on the charts for 1gpm/ Should the company be liable? I kept the old pump an dit is a 3/4 hp pump?? Thanks
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