I can't speak for Jon, but I'll offer that RL-10X being about three notches slower than H322, is a bit better suited to the 204 case. I use H322 with excellent results in my .17 Mach IV, and it's also good in the 221FB and 20VT.....all in a the smaller FB case. I don't shoot the Berger 35gr much, as most of my shooting is volume affairs at ground squirrels and PD's (and the occasional rockchuck of course), so the 32's get the most action.
But RL-10X has proven to be the powder of choice for both the 32's and 39/40's in all four of my 204's. H4895 may be a better choice for the 40's, as it gives excellent speed along with very good accuracy. But here's a random target shot with RL-10X after a Cooper/Jard trigger replacement:
My other 204's all seem to thrive on RL10X too. But at this point in time, you'll be well advised to work up decent field loads using at least two powders, as FINDING the stuff can be probematic. Always nice to have a Plan B.
