.423 Van Horn

.423 Van Horn

The .423 Van Horn is an obscure but fascinating wildcat cartridge developed primarily for use in single-shot and specialty handguns. Originally designed by Richard Van Horn and explored in the March 1982 issue of Handloader magazine, this cartridge was an attempt to blend the performance of high-power medium-bore rifle cartridges with the portability and manageable recoil required in handgun platforms, particularly the Thompson/Center Contender and similar break-action firearms.

The .423 Van Horn is based loosely on modified cases — often derived from .30-06 or similar parent brass — necked up to accept a .423" bullet (approximately 10.74mm). The cartridge is notable for its ability to launch heavy-for-caliber bullets in the 300 to 400-grain range at moderate velocities, producing excellent penetration and energy delivery at close to medium range. It was designed with big game in mind — particularly wild boar, elk, or bear — and its performance in a properly built single-shot platform was intended to rival that of lever-action rifles using .444 Marlin or even .45-70 class ammunition.

Reloading data for the .423 Van Horn is limited due to its niche status, but published test loads indicate it operates at safe pressures for strong single-shot actions. Common powders include IMR 3031, H4895, and Reloder 7, with cast or jacketed bullets in the 325–350 grain range. Muzzle velocities range between 1,700–2,000 feet per second depending on barrel length and load, producing energy suitable for medium to large game.

Due to the uncommon nature of the cartridge, forming cases requires resizing and trimming from available parent brass. Dies for the .423 Van Horn were custom-made and may still be available through specialty die makers or custom reloading equipment providers. Shooters must take extra care in neck expansion, bullet seating, and chamber dimension matching when working with wildcats like this.

Though not widely known or adopted, the .423 Van Horn represents the kind of creativity that defined much of the late 20th century wildcatting scene. It appealed to those seeking powerful, accurate hunting performance in compact, single-shot handguns — especially for backcountry use where every ounce counts. Today, it holds niche appeal for collectors, custom handgun enthusiasts, and fans of big-bore experimentation.

For a full breakdown of performance data and background on its development, see the original article in Handloader No. 96, March 1982.