20/577 Alexander Henry

The 20/577 Alexander Henry, also known as 20/577 Express, is an obsolete rifle cartridge.

20/577 Alexander Henry
Type	Rifle
Place of origin	Scotland
Production history
Designer	Alexander Henry
Designed	1895
Produced	1895
Specifications
Parent case	20 bore
Case type	Rimmed, bottleneck
Bullet diameter	.584 in (14.8 mm)
Neck diameter	.607 in (15.4 mm)
Shoulder diameter	.674 in (17.1 mm)
Base diameter	.706 in (17.9 mm)
Rim diameter	.754 in (19.2 mm)
Rim thickness	.06 in (1.5 mm)
Case length	2.75 in (70 mm)
Overall length	3.27 in (83 mm)
Ballistic performance
Bullet mass/type Velocity Energy 560 gr (36 g) UNK UNK 570 gr (37 g) 1,725 ft/s (526 m/s) 3,770 ft⋅lbf (5,110 J)
Source(s): The big game express[1] & The Spanish Association of Cartridge Collectors[2]

Overview

The 20/577 Alexander Henry was developed and introduced by the Scottish gunmaker Alexander Henry around 1895 exclusively for his hunting rifles.^{[1][2][3][4][5]}

The 20/577 Alexander Henry is a rimmed, bottlenecked centerfire rifle cartridge. The 20/577 Alexander Henry is derived from brass 20 bore cartridges necked down to accept a .584 in (14.8 mm) calibre bullet like the .577 Black Powder Express.^[1][2][4][5]

The 20/577 Alexander Henry fired a 560 or 570 gr (36 or 37 g) lead, paper patched bullet driven by 6 drams (10.6 g) of blackpowder at 1,725 ft/s (526 m/s), its ballistic performance replicating that of the .577 Black Powder Express 3-inch. Later versions were loaded with mild loadings of cordite, carefully balanced through trial to replicate the ballistics of the blackpowder version, a copper-tubed lead bullet was also available, offering improved performance against dangerous game.^{[1][2][3][4][5]}

See also

• Express cartridges
• List of rifle cartridges
• 13 mm caliber