Chuck Hawks
Mr. Hawks has a pretty good write-up of the Rem 600 on
his site here.
In summary, the Rem 600 rifle is based on the XP 100 pistol action. Hence the dogleg bolt required in the pistol to have the bolt handle forward of the firing hand for ergonomics.
The 600 was seen as a lightweight fast handling carbine. Barrel lengths were usually 18.5" and chambered in .222 Remington, .223 Remington, .243 Winchester, 6mm Remington, .308 Winchester, and .35 Remington. The 600M (Magnum) was also offered in 6.5 Remington Magnum and .350 Remington Magnum with 18.5" barrels.
Many folks disliked it because the ventilated rib on the barrel, the magazine floorplate, and trigger guard were all made of plastic. Many Rem 600s on the shelves of dealers today have severely warped floorplates and it is repairable by replacing the unit with a steel version available aftermarket. The Remington 673 does not have the infamous plastic parts of the 600.
The Rem 600 action is very close the the Model Seven in dimensions, but with the XP-100 pistol action's bolt.
Hope this helps a little!