Notes: One of the largest Swiss "small arms" in existence, the OM-50 was the brainchild of James Owens (a retired USMC officer), and Chris Movigliatti, a retired Swiss Army officer. They formed a new company in Switzerland, AMSD, to manufacture the Nemesis (and perhaps in the future, other weapons – the two reportedly have a slew of other ideas). The ideas for the Nemesis had been kicking around with the two for quite a while; as a result, the first prototype of the Nemesis appeared only 3 months after official design work began. The Nemesis features a modular design, allowing it to be customized to user needs or made in military, police, and civilian versions. Supposedly, the Nemesis is already being tested and possibly used by a number of agencies, but it did not enter low-rate production and sales until 2003.

Construction of the Nemesis is a mix of high-grade aircraft-quality aluminum (primarily in the receiver housing and some other exterior metalwork) and high-grade steel. The stock is sort of skeletonized, but highly adjustable, including an adjustable, padded cheekpiece (adjustable for height and angle), and an adjustable buttplate with a recoil pad (adjustable for length, height, and to a small extent, angle). Mk 1 stocks are otherwise fixed, but Mk II and Mk III stocks are side-folding. Barrels are easily changed and may range from 15 to just under 33 inches, and may be swapped out as necessary for the tactical situation or local laws. (A barrel change takes about 2 minutes and requires a flat-head screwdriver or an equivalent). The barrel locks directly onto the barrel extension, and is otherwise free-floating. The standard muzzle attachment is a high-efficiency muzzle brake, but threading at the muzzle allows for many other muzzle attachments. The trigger unit is fully adjustable (length of pull, pull weight, and angle) and is two-stage. The top of the receiver has a MIL-STD-1913 rail. No iron sights are provided as standard.

The Mk I configuration is intended primarily for civilian shooters; it is a bolt-action single-shot rifle with (other than mentioned above) a "basic" configuration. It can easily be converted to the Mk II configuration, which gives it feed from a box magazine, a retractable monopod on the butt for long hides, a folding bipod adjustable for height and cant attached at the front of the handguard, and the side-folding stock. (The bipod can also be added to the Mk I configuration, though it is not normally sold with a Mk I rifle.) The Mk III is basically similar, but adds short MIL-STD-1913 rails to either side of the forward receiver, and special threading allowing the use of a suppressor in addition to other types of muzzle attachments. It can also fire special ammunition designed for use with a suppressor. The Mk II is quite similar to the Mk II for game purposes, except when firing with a suppressor; in addition, a kit allows the top MIL-STD-1913 receiver to be extended nearly to the muzzle.

Twilight 2000 Notes: The Nemesis does not exist in the Twilight 2000 timeline.