New to Java

Ok... I'm not new to Java... just new to Swing. I'm frustrated with how some of this stuff works, and I was hoping someone could clear this little bit up for me.

I've got a JButton. I want to wipe away the margins and set the size of the margin as I like. However, depending on the layout of the JPanel, I get different results for the same lines (that should in my mind do the same thing)... Here are the lines in question.

   import javax.swing.*;
   import java.awt.*;
	
    public class XXXXXX extends JFrame {
   
       public XXXXXX()	 {
       
         //...
         
         JPanel panel = new JPanel();
         getContentPane().add(panel);
         panel.setLayout(null);
         
         JButton sendMsgBtn = new JButton("Send");
         sendMsgBtn.setBounds(200, 60, 50, 30);
         sendMsgBtn.setMargin(new Insets(0,0,0,0));
      
         panel.add(sendMsgBtn);
      }	
   
   }

When I comment out the panel.setLayout(null) line of code then the setMargins works (but the setSize part of the setBounds doesn't work). However, when I leave the line uncommented, the setSize part of setBounds works (but the setMargin doesn't work). Any ideas?

I guess the pertinent question would be this... Why doesn't the setMargin() call work since I've set the Layout to null?