Tell your friend to borrow a muzzleloader or a .22 magnum.

According to the way i read GA hunting regs, .22 rimfire rifles are legal to use in small game season; that includes the .22 magnum. The state of OK has the same hunting rules in WMAs during small game season; small shot or rimfire rifles. Ft. Sill has the same rules during small game season. i've killed several dozen hogs with a .22 magnum and it works very well if you limit your shots to 50 yards or so. A couple of those hogs weighed over 300 pounds on the hoof.

Wait until the hog is broadside and put the bullet in it's ear. Don't shoot a hog behind the ear because there a good chance the bullet will miss the brain. i sometimes shoot smaller hogs low just behind the crook in the leg, this takes their heart out. Hogs are not built like deer.

Hog anatomy:

http://www.texasboars.com/anatomy.html