Are you plunging right through full depth and cutting it in one pass, or do you have a finish allowance?
A 3/16 endmill does not have a lot of flute space, so it can clog. For full width cut from the solid, I would estimate you can bump your rpm up (if available), reduce the depth of cut to .046" per pass, bump feedrate up to 20 ipm (for starters), and leave a finish allowance of about .005 for the final profile.
It would be best to ramp down to cutting depth with a center cutting endmill, although plunging .046" at a time is not too awful, any vertical plunge cuts should be done a small distance away from the finish profile, because the tool will wobble around. An endmill is not as stable as a drill, because it has no conical point.
A 4 flute endmill might not be center cutting (you did check that before you used it, right?
), but chances are that it is incapable of clearing chips during the plunge. A ramp or helical entry into the part greatly improves the tool life.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)