Rick, I do something similar with my pine bark.
I get bags of pine bark fines, not nuggets.
The biggest pieces get screened out and become mulch for the outdoor beds. The medium pieces become potting mixes, with a bit of compost and perlite added to them. The super fine pieces I'm using to sow seeds.
The screening process is more work, but it's so much cheaper than buying potting mixes. Last year I used commercial seed starting mixes for wintersowing, but they were so compacted and almost slimy after a couple of months.
I actually like the fact that they dry out faster in the pine bark mix.
