no problem. we've had a 20 gauge single shot pardner in the family for almost 20 years & it still works great. i'd recommend a recoil pad since these guns are fairly light & can kick like a mule with heavy loads.
H&R's barrel program also let's you put a different gauge barrel on the same receiver, so if you bought a 12 guage & want to shoot 20 gauge or get a rifled slug barrel, send it to them & they will fit another another one.
All I've had today is like 6 gummi bears & some scotch