Hi David, Both have exactly the same components. I couldn't find anything different in the specs. The only difference is the UPC so i believe they're the same firearm besides the caliber SPECS-- •Semi-auto Multi-Purpose Weapon (MPW) •Corrosion-resistant SCARmor™ chamber coating •Heat-treated & properly staked carrier w/Permatex® gasket-seal compound ensures no gas leakage key •Nickel-Boron coated carrier & cam pin •Shot-peened & black phosphated Mil-Spec Carpenter 158® bolt •“Full auto” bolt carrier group features an added base layer of high-phosphorous electroless nickel to ensure extreme corrosion protection •Custom 383K psi steel extractor spring & 300 ksi S2 tool steel extractor pin •Wide temperature range green O-ring (tested to -40°F) •Pictogram-marked lower features Geissele 2-stage trigger & Magpul® trigger guard •4150 CMV steel threaded barrel w/corrosion-resistant SCARmor™ bore & exterior coating •1:7&q

almost all the parts are identical

Other than the rail system, these are identical builds David.

The 101997 rifle comes with the URXIII Rail instead of what is shown per a review at the bottom of the product page