Wait, you confused me.
Standard logic is that when crimes are committed with legal guns, that argues for more gun control laws- since perhaps the guns would not have been in their hands if it was illegal.
When crimes are committed with illegal guns, that argues that gun control was ineffective and so is pointless, and if anything makes it more dangerous for the law abiding who are unarmed.
You are adding a twist that perhaps the penalties are just not strict enough.
In NY, criminal possession of a weapon has 4 degrees, and ranges from a class A misdemeanor to a class B felony. The penalties range from a maximum of one year on prison to 25 years in prison. Additionally, most offenders will usually fall into at least the second level, since if you have previously committed any crime (and illegal gun owners probably have), it is at least 3d degree which is a class D felony.
What would you like the punishment to be?