Standard factory 222 Remington ADL has a 1/14 twist rate.
The twist rate is 14"
1 in 16"
1/12 or 1/14.
The value of a Remington model 600 .222 caliber depends on the condition of the gun. One in excellent condition is worth approximately $500, as of 2014.
$500-$600
remington 725 caliber 222 bolt action excellant condition
Remington, Winchester, Sako to name a few
400 USD
That really depends on the condition. Take it to a gunsmith or appraiser or go to auctionarms.com to get an idea of what they are selling for.
The Remington model 720 rifle was never offered in the 222 chambering. While it would have been technically possible to convert, the work required would have been totally out of any reasonable proportion to the result. Perhaps you actually intended to refer to the Remington Model 722 which was produced in that caliber. Price guides area available for reference to the current value for one of these rifles.
22 is a rimfire, 222 is a centerfire.