Jason Hommel has been doing just that. He's sold some of his 100 oz. bars at auction making some profits on the sale and then reduced his replacement cost with the 1000 oz. silver Comex bars.
However his source for 1000 oz. Comex bars has just run out.
Please note I did NOT say the Comex ran out.
An individual cannot just buy a bunch of contracts and take delivery or the Comex would probably be gone by now. They have limits on phsyical delivery that they will allow you to take.
Its a nice game you sell all you want of what you don't have; but you can't buy what you want if you actually want to take it.
P.