| Mechanical system | Spring piston, single shot | |
| Caliber/Ammunition | RM277/RM377/RM577/RM777: .177 cal. (4.5 mm) Lead Airgun Pellet RM522/RM622: .22 cal. (5.5 mm Lead Airgun Pellet) | |
| Total length | RM277/RM377: 39 in. (99.06 cm) RM577/RM777: 45 in. (114.3 cm) RM777: 48 in (119 cm) | |
| Weight | RM277/RM377: 7 lbs. 1 oz. (3.2 kg) RM577/RM522/RM622: 7 lbs. 15 oz. (3.6 kg) RM777: 8 lbs. 4 oz. (3.74 kg) | |
| Muzzle velocity | RM277/RM377/RM522/RM622: Up to 825 fps (251 m/s) RM577: Up to 1000 fps (305 m/s) RM777: Up to 1100 fps (335 m/s) | |
| Function | Break Barrel | |
| Barrel | Rifled Steel | |
| Safety | Automatic ambidextrous |