I wouldn't run the risk. Is that 4 3/4 dram 1 5/8 oz? I reload for my 2 7/8 ten 1 1/4 oz @ about 1200 fps. RST makes crackerjack 10 gauge shells just right for your Parker. As a side note I have a box of WW 2 7/8" 4 1/4 dr 1 1/4 oz of 4's that I keep.
Kindest,
Harry
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