I would try dialing up that RPM. I assume that you are running that face mill in mild steel? If so, then try 1200 RPM so you can get your SF/M to up 600ish. Then, feed the mill according to what gives the best results. I would do a DOC of something like .005".
That seemed like such a fast speed, considering the size and number of cutters, even more than I use for a regular end mill of much smaller size. But I'll give it a shot tomorrow and see what happens.
Whoops sorry I missed that @tonydi
No problem, David. I get wordy and so I'm used to some of my info getting lost.