WASHINGTON — The Senate Judiciary Committee on Thursday approved a measure that would make the practice of illegally buying a gun for someone else a felony, and increase penalties for the crime.

The measure, which addresses a practice known as straw purchasing, passed the committee by 11 to 7; the only Republican to vote in favor was Senator Charles E. Grassley of Iowa. Mr. Grassley’s nod on the measure, which already had two Republican co-sponsors, was significant because he is the most senior member of the committee. The panel is made up of 10 Democrats and 8 Republicans.

Some Republicans on the committee spoke out against the bill, including Senator John Cornyn of Texas, who said the legislation seemed intended “to show we are doing something,” but in the end would not be effective in halting gun crimes.