big bore ?
 

I have been kicking the idea of getting a large bore air rifel has any one ever yoused one and if so what are the draw backs to them.

I can`t help you, but if you get one please give us a report on it. I have had a hankering for one ever since I saw a 9 mm air gun while up in Alaska. It fired a 129 gr. cast bullet through 1 pine 2x4 and into the second. Very impresive. At least I thought it was.

I have seen show were they have killed hogs and sheep with them.

Why bother ? you will need a air tank to keep it pumped up and powder burners will out perform it in all departments for a lot less money