I have a remington 788 in .222 but would rather have a remington 700. My local wal mart has a remington 700 in matte black in 223 for 400 bucks. Could a person buy the remington 700 in .223 and have a gunsmith re chamber it to .222?

Sure.

Yes, but you would have to have the barrel set back some. I am not sure how much. The 222 is shorter than the 223.

I have encountered several 222s that had been rechambered to 223, but never vice versa. Is this 700 at Walmart a 700ADL or
a 700SPS?

this gun is an older version of the adl. It comes as a combo with a cheap scope.

Go to a .222 Magnum. I believe it's longer than the .223.

Yes, but the barrel would have to be removed, the shoulder set back ,threads added to , shank shortened, conterbored ,chamber reamed to 222 and then intalled and re headspaced. Might will cost as much as doing setting up a new barrel.

Just take the money you would spend on rechambering a .223 to an inferior cartridge , and buy .223 ammo and a set of dies . Then you'll have a 700 that isn't devalued due to rechambering to a cartridge that is all but obsolete . There is nothing a .222 can do , that a .223 can't do better ! JMHO

I have a remington 722 in .222 I would trade you for your 788.

And be careful that the Wal Mart 700 is not really a 770.