shot gun barrels only on SB1 frames. Assuming the gun he has is all original then he can NOT have a rifle barrel fitted to it. This is covered in the FAQ's. If you go to the H&R web page, then customer support, then accessory barrel program, it will tell you what barrels can be fitted to which frames. Most rifles have SB2 frames, there are some exceptions like the 357 or 44 rifles which carry a warning about this. JamesIII