I've felt like I've snagged something while inserting a pin before... Like scar tissue or something. Didnt really "pop" but could feel the pin go through...
I prefer inserting the needle slow.
I think there is less trauma by inserting slowly then fast.
The medical community does some stuff that doesnt always make sense...
Like injecting squarely in the middle of the quad.
Go high to the outside....less pain.