If you do not go deep enough, you will not hit the muscle layer and the absorption will be poor. You want the gear to hit your body in 2 hours, especially if you are using pure test. If it goes into the fat layer, the absorption will be longer and poor distribution over-all. Hence, push that 1.5" pin all the way in. I prefer a 1 inch pin in the delt. I just can not bend around to hit the back ... I start to cramp up at times.
I once asked a buddy this.
"Can they come up with a better way to give injections in the a$$, I just can not do it anymore. Someone should come up with an invention for this."
His reply ... "Yea they have one ... it is called your wife or your buddy."
He stabs it in always ... I am the kind who has to push it in slow. It does not hurt but I just can not stab it in like a monster.