The Henry Big Boy Mare's Leg SG is a .44 Magnum lever-action pistol with a 12.9-inch octagonal blued barrel, polished hardened brass receiver, American walnut stock, and a side gate for loading. Overall length is 25 inches and weight is 5.79 lbs. Capacity is 5+1 rounds. 
 

Key Specifications 

• Caliber: .44 Magnum 
• Action: Lever Action 
• Capacity: 5+1 rounds 
• Barrel Length: 12.9 inches 
• Weight: 5.79 lbs. 
• Sights: Semi-buckhorn with diamond insert 
• Barrel Type: Octagon Profile 
• Finish: Polished Hardened Brass Receiver; Blued Barrel 
• Stock Material: American Walnut 
   

Detailed Features 

• Side Gate: Loads individual rounds directly from the receiver side, faster and more intuitive than muzzle-end tube loading. 
   
• Transfer Bar Safety: The firing pin is isolated from the hammer unless the trigger is fully depressed, allowing safe carry with a chambered round. 
   
• Octagonal Barrel: Traditional aesthetic and structurally stiffer than a round contour of equivalent weight. 
   
• Fully Adjustable Semi-Buckhorn Sights: Adjust for windage and elevation; the diamond insert improves sight alignment in lower light. 
   
  The .44 Magnum in a 12.9-inch barrel generates meaningful recoil -- more than the .45 Colt version of the Mare's Leg due to the higher-pressure cartridge. Velocity is lower than a rifle-length barrel but still capable for short-range applications. The pistol classification means an FFL transfer is required. Note that .44 Special can also be fired in a .44 Magnum chamber for lighter practice loads.

The .44 Magnum Mare's Leg SG gets consistent praise for its look and the quality of Henry's brass-and-walnut finish work. The side gate is seen as a practical addition over the original Mare's Leg design, making the gun more useful for actual shooting rather than just display.

The .44 Magnum caliber draws a range of responses. Shooters who want a capable short-range tool appreciate the cartridge's power. The recoil in a 5.79-lb. pistol-length configuration is noticeable with full-power loads, and some users prefer shooting .44 Special or downloaded .44 Magnum loads for extended sessions. The shorter 12.9-inch barrel reduces velocity relative to carbine or rifle configurations.

Ergonomics discussion is consistent across Mare's Leg variants: the configuration suits some shooters naturally and feels awkward to others. Comfort for extended shooting varies more by individual hand and grip size than with conventional pistols or rifles.

Accuracy at close-range distances (25-50 yards) is reported as satisfying for the format. The fully adjustable sights help shooters get on target with specific loads.

Buyers are fairly candid that the pop-culture connection -- the Mare's Leg's association with TV Westerns -- was part of the appeal, and most are comfortable owning something that's as much a fun range piece as a practical tool.