i was pressing pretty hard, but it still came out. i guess one (or both) of two things going on, enough grease in there, and instead of it squirting out the caps, pressure came out from needle contact surface to zerk, or i wasn't holding it square enough on the surface of the zerk, and it was squirting out the side.
try, try, again.........

 

Try poking the little ball down with a tiny Phillips screwdriver. Sometimes they get stuck.

If you can't get any grease in there its probably full.

On new u-joints when they are full they usually spit the grease back out the fitting, on older joints it all comes out of the caps.