Missouri Regulations are as follows;
Methods allowed during all portions of the firearms deer season, except the muzzleloader portion.
•centerfire pistol, revolver or rifle using expanding-type bullets. Legal ammunition includes lead bullets, copper bullets and bullets made of other material designed to expand.
•shotgun (including .410) with slugs only
•air-powered gun, .40 caliber or larger, charged only from an external high compression power source (external hand pump, air tank, or air compressor)
•a muzzleloading or cap-and-ball firearm .40 caliber or larger and capable of firing only a single projectile at one discharge; in-lines and scopes are allowed
•multiple-barreled muzzleloading or cap-and-ball firearms and/or muzzleloading or cap-and-ball handguns, including revolvers, .40 caliber or larger are allowed and may be carried in addition to a muzzleloading or cap-and-ball rifle
•a longbow, compound bow or recurve bow of any draw weight; hand-held string releasing devices, illuminated sights, scopes and quickpoint sights are allowed
•crossbow
•atlatl, which is defined as a rod or narrow board-like device used to launch, through a throwing motion of the arm, a dart 5 to 8 feet in length.
Methods prohibited (in use or in possession)
•self-loading firearms with capacity of more than 11 cartridges in magazine and chamber combined
•ammunition propelling more than one projectile at a single discharge (such as buckshot)
•full hard metal case projectiles
•fully automatic firearms
•any sighting device that casts a beam of light on the game
•electronic calls or electronically activated calls
With that said, a RBH .357 fits the bill just fine. I am leaning towards a 6.5" stainless model.