I shot a few rounds of 20 grain factory in mine just for a base line, I had a pile of once fired brass gifted to me.
I read, then read some more. Then I read more.
I saw very few powders that didn't get touchy at the top end, then some would go squirrelly with no warning.
I went out and bought a few powers I didn't have on hand.
Sat down, did some more figuring. Started off with H4198. Loaded a ramp and went to the range. After shooting these I found a node and went with it. I gave up a little speed, but the accuracy was sure there. Honest, consistent .5 groups and not much more at 200 with good conditions.
Load is still under book max, have no idea how the got the other half grain in the case. I am using a B&M measure and a 12" drop tube and still never got their max load into the case.
As to OAL, the blasted CZ mag determined that. I can single feed with the bobsled but it still doesn't work as well as the magazine.
FYI 25's did shoot as well but I did not see the results on critters that I liked. So I save the 25's for the 17 Remington.
I am tinkering with a Bmag 17WSM. If I can get it to shoot MOA it will replace my 17 Hornet for shots out to 200.
Jeff