Handgun type used on Sikhs is mass shooting weapon of choice

[OneTenthofOnePercent]

24. But what's the basis or cut-off point for such legislation? Where is the "line in the sand"?

IMO, you need a solid starting point and basis/justification for a gun debate.
a) Determine the necessity for action - (the need to limit firepower has been illustrated)
b) Determine what item needs limitation to satisfy the necessity for action - (magazines limits will limit firepower)
c) Determine Limitations - ( ... ??? ...)

High capacity magazines are bad. Got it. Why? Because they allow a shooter to achieve maximal amount shots fired in a minimal amount of time. OK, I get that too. So if one suggests a ban or (as you recommended) stricter scrutiny in sale on these hi-cap magazines...

My question is, "If limiting the maximum amount shots fired in a minimal amount of time is the goal... what should the magazine limit be (ie: shots per second) to determine which kinds of magazines receive extra legal hurdles? 3 rounds, 10 rounds, 15 rounds, 20 rounds, 30 rounds ... ?"