I have had the same problem in the past. I'm not the best guy to give you spray paint advice but you need to check the air pressure pattern adjustment at the gun as well as the liquid flow adjustment.

If you tried painting this past weekend in So-Cal, it was HOT and you might need to thin out the primer some so it does not dry as soon as it hits the surface. I shot PPG high build two part primer on my frame on Sunday and had to use just a little acetone to slow it down for it to lay down and smooth out.

I'm sure someone will explain it in better terms.