I've never had a .204R. But have been playing with .20's since long before the .204R existed. My experience with the 39BK on coyote has all been at much higher velocity. From about 4,000 to 4,300 fps. At much above 4,000 they have been pretty much a fail. Just too splashy. At 4,000, I have gotten mostly bang flops. But, the occasional splash/runner too. Erratic performance, in other words. I've given up on them as a Big Twenty coyote bullet. Although, I'll go ahead and use up the ones I still have loaded, maybe 30 rounds or so. Because, they have been "mostly" bang flops.
At only 3,450 fps I don't think splash will be of any concern. And I'd just purely guess you'll get more consistent, less erratic performance. I'm just guessing they'll kill like gangbusters. Only one way to actually know though...
- DAA