Is there a command or setting that I can change so autofill puts 50 or 100 bullets in a turret when placed? Default appears to be 10 for a turret but as I get better established it would be nice to change the default.

Open the Zip file. Settings folder. vanilla-sets.lua. Change line 20.

Defualt
["gun-turret"]= {priority=order.default, group="turrets", limits= {10}, "ammo-bullets" }

Replace the number after limits with whatever you want it to be.

This doesn't seem to work, I've tried modifying the integer from 10 to 30 but when I fire the game back up it still drops 10 bullets into the turret. Any suggestions?

You can open/edit the file while it's in the zip folder, but on my PC I was not able to actually save over that file. Instead I copied the vanilla-sets.lua file to my desktop, modified it there, and then dragged it back into the zip folder to copy it over the old file.