I use Winchester AA Featherlites (Xtralites?) one step above Low Recoil/Noise shells in my twist barreled American made hardware store gun with no problems (still got all my fingers). Seriously, with no proof houses I think a lot of American manufacturers went by the old adage, if some is good more is better, when it came to barrel thickness (and to hell with the poor guy who had to carry the thing all day).
Steve

Approach life like you do a yellow light - RUN IT! (Gail T.)