True, but it isn't that hard.
Do you know this for a fact? Or just speculating. Why don't you ask Zimmerman how much his legal fees are expected to be after he shot someone who was apparently beating his head against concrete. In that case, the guy had a CC permit, appeared to have been attacked and beaten, shot in self defense with an ordinary gun......and the prosecutors are kneeling and praying with the perp's parents frothing at the mouth to get a conviction.
Folks around here are skittish about doing ANY modifications to a stock weapon for self defense, for fear that some over zellous prosecutor will make them look like someone who is out to hunt human game. We're talking springs, sears, & triggers. Not suppressors used by Russian Spys to silently assasinate sweet inocent little girls who saw too much. (not my words....just the words of the prosecutor who will be handling your file).
FWIW, I'm 100% pro-2nd Amendment, pro-machinegun, pro-suppressor. I wish folks could use these in truly defensive situations without threat of costly prossecution. But, that's not the country we live in today.