Notes: The APH RK-97 is a single-shot heavy rifle designed in two versions chambered so that exports will be attractive to virtually any country in the world. Externally, both versions look identical, with a semi-bullpup-type layout (some of the action is in the stock, but some is more towards the center and some in forward of the pistol grip). The stock is of light alloy that is essentially the bare minimum required to enclose the part of the action which is in the stock; attached to this is a raised synthetic shell-type cheekpiece and a padded buttplate. At the front of the forward portion of the receiver is a folding bipod of fixed height; however, the bipod can be partially-folded and locked at different angles, providing a modicum of height adjustment. The very long 44.4-inch barrel is made from heavy steel, and is tipped with a large pepperpot muzzle brake. The muzzle brake can also be removed, revealing threads which can be used with most of the (very few) suppressors available for the ammunition the APH RK-97 fires. The APH RK-97 has no factory-installed iron sights, though it does have attachments points for them; the APH RK-97 is meant to be used with telescopic sights. A scope is attached to standard ring-type mounts, which are mounted on a bracket which attaches to either side of the weapon above the pistol grip.

The strangest part of the APH RK-97 is its vertical dropping breech block operation. The APH RK-97 is breech-loaded, but the action is operated by moving the foregrip in sort of a pump-action. The fore-end is pushed forward, opening the action and allowing the shooter to load a cartridge; then the fore-end is pulled back, raising and locking the breech block.

The APH RK-20 is essentially the APH RK-97 scaled-up to fire a much larger round – the World War 2-vintage Russian 20x99mm ShVAK cartridge (originally designed to be fired from aircraft-mounted cannons of the period; the cartridge is known to the Finns as the 20x100mm Swak). Other than the larger size of the action, receiver, the diameter of the barrel (even though the barrel is much shorter at 33.9 inches), and a larger and heavier pepperpot muzzle brake, the APH RK-20 is essentially identical in design to the APH RK-97.

The RK-99 is essentially an updated, magazine-fed version of the APH RK-97; externally, it looks a bit different, with a more squared receiver and action housing, and the shorter 32.4-inch barrel. Internally, of course, the RK-99 is very different than the APH RK-97, due to its repeating action; when the "pump" action is used, a round is pulled into the chamber and the action locks via a rotating bolt; after firing, the spent round is ejected normally, like that of the APH RK-97. The 5-round magazine is standard; 10-round magazines are available, but tend to present a "third leg" problem due to the size of the magazine and the bullpup layout, and are therefore not normally used. The RK-99 was not introduced until 2000, as opposed to the APH RK-97 and APH RK-20, which were introduced in late 1997.

More or less related to the RK-99 is the RK-99MK1. The RK-99MK1 is a single-shot rifle, but actuating the "pump" mechanism drops the entire bolt carrier assembly out of the bottom of the receiver; the bolt carrier includes a shell holder for the cartridge. After inserting the cartridge, the bolt carrier assembly is re-inserted into the receiver and the "pump" slide pulled back to lock it into position. After firing, the bolt carrier is again dropped out of the rifle, with the expended shell being ejected separately. This operation allows more positive locking and greater reliability in a single-shot weapon, as well as allowing greater flexibility in using different ammunition types, but also greatly slows down the reloading of the weapon. The RK-99MK2 is basically identical to the RK-99MK1 (except for the changes required for the different caliber and a shorter 31.5-inch barrel), but is chambered for the 20mm ShVAK cartridge.

Twilight 2000 Notes: The APH RK-97 and APH RK-20 were not known to be used outside of Finland in the Twilight 2000 timeline; even in Finnish service, they are rarities. The RK-99, RK-99MK1 and RK-99MK2 do not exist in the Twilight 2000 timeline.

Merc 2000 Notes: The APH-RK-97 is a big seller around the world, particularly chambered in .50 Browning Machinegun; the APH RK-20 is less popular, mostly due to the greater weight, recoil, and relatively limited applications. The RK-99 is even more popular than the APH RK-97; the RK-99MK1 and RK-99MK2, less so than even the APH RK-97 and APH RK-20.

*Penetration against personnel is 2-2-3.