Governor Deval Patrick is again appealing to Massachusetts lawmakers to approve his sweeping gun control bill.

Patrick is planning to testify before a hearing of the Public Safety Committee at the Statehouse today.

The committee has been holding hearings on nearly 60 gun-related bills across the state this summer.

Patrick's legislation would tighten access to high-powered rounds of ammunition, create four new types of firearms-related crimes and mandate that buyers undergo background checks before purchasing weapons at gun shows.

Critics say the bill goes too far and would punish law-abiding gun owners, and gun rights advocates plan to speak out.

Before the 10 a.m. hearing, supporters of tougher gun measures plan a press conference in front of the Massachusetts House chambers. They include parents of children killed at Sandy Hook Elementary School in Newtown, Conn.