15 SECONDS is pretty quick...
1.5 cc takes me about a minute with a 25g...slow and steady pressure.
if you aren't injecting deep enough you might get a lump.
He's right. If the pin is not deep enough, then there can be a slight problem. For spots like delts, bi's, tri's, lats, pecs, etc, a 1" pin is normally fine. For glutes and in some people quads, a 1.5" is better. Of course if you are holding a lot of fat in a particular area, no matter where it is, you would be better off always using a 1.5". I myself use 1" inch every where except glutes, my quads never hold much fat at all...now if I could just get my mid-section to follow suit when bulking then dieting would go so much easier...but oh well, that's genetics.