It's very common for games to copy guns and just give them a new name

See Goldeneye from 1997 which renamed the FN P90 to RC-P90 amongst a whole slew of other guns. Perfect Dark did similar things including also having the FN P90 but now named RC-P45 in addition to the RC-P120.

Timesplitters 2 also did this with the SBP90.

It's very common for games to copy guns and just give them a new name

See Goldeneye from 1997 which renamed the FN P90 to RC-P90 amongst a whole slew of other guns. Perfect Dark did similar things including also having the FN P90 but now named RC-P45.