For the record, some of the guns had additional fluff attached to them, though introducing them in "Similar Models" one-liner wouldn't have allowed to make mention it.
Fleche PC Seraphim (equiv. SA Puzzler): PC stands for "Pistolet Composite". Fleche Armaments was a Cross subsidiary, the Seraphim where Cross spooks, it's equivalent to the SA Puzzler, you connect the dot.
Colt Rattlesnake (equiv. Ares Crusader): I originally came up with the name for a a gun I drew on a character sketch... in the mid-1990s. It supposedly suffers from an flawed ejection port design that may result some times in injury... as a result of me redrawing that part of the gun several times without achieving a look that satisfied me.
Ares A11G1 (equiv. AK-98): There ought to be an Ares A11 equivalent to the AK-97, but I wouldn't have had the opportunity to introduce it (since the AK-97 is not featured in Arsenal). Ares Small Arms only assault rifles listed were the Alpha and the HVAR, which both include smartlink and special features and cost several thousands nuyen. The A11 would be the rifle Ares sells to Third World armies and the likes (though I guess they could also deliver AK-97 or Colt M-23 when they want to support such local factions for political or economical reasons, and keep a higher quality standard for the Ares brand).
Taurus MD-50LE (equiv. AK-98): Same thing, the standard MD-50 would be equivalent to the AK-97. IRL, Taurus is a Brazilian manufacturer. The MD-50 would be standard issue for eco-terrorists trained in Greenwar-run, Amazonian gov-backed boot camps.