Joe,
None of the bulk dealers around here want to carry stove size. just not enough demand to be driving their 18 wheelers down to PA to get a load. One dealer does carry some bagged Blaschak stove, but it costs more.
In some Glenwood literature it recommends stove size coal for their ranges. So, I tried a few bags of that Blaschak stove a while back. Those bags also contained a wide range of sizes on down to lots of fines and puddles of water and fines slurry in some of the bags.
While just using stove size, it burned well and gave slightly higher heat volumes for the oven. Plus as you'd expect with the easier breathing firebed of stove size, it was quicker to response to damper setting changes than nut. But, it did not last as long.
Back when we were doing the Glenwood #6 magazine project I did a lot of measuring stove verses nut coal in the same space. It showed there was a difference of 10% by weight between the two sizes. My range's fire box holds about 20 pounds of nut, but only about 18 pounds of the stove size.
So, just using stove coal, I found that I had to check and add coal more often while cooking/baking dinner. And, all that's involved in doing that sorta displeases the cook when she's also trying to work at the stove.
It doesn't take a genus to know that if you want good food, don't do things that make the cook mad !
That experiment pointed out that with the strong drafting chimney I have (built back at the height of coal use)stove size coal didn't help without it also having a downside. So, by better management of the dampers, nut coal works very well and lasts longer between refueling. And more importantly, the cook was happy.
However, if I had a weaker drafting chimney system, then I'd likely use stove, or at least a mix of stove and nut.
Pauyl