We had IR aiming lights for our M203's as early as OIF III. A few of our enlisted Soldiers who were RFS'd from the Rangers said that they had them a couple years before that. So long as you estimate range within the ballpark (which you need to do anyway if using leaf or quadrant), it's very accurate. Even in training, guys who had never fired a 203 before (really, we had a bunch of people who had never fired one - unbelievable) they were scoring first-round hits on targets at 250 meters at night. It was kind of bulky, but lightweight. I think the latest generation are far less bulky and even lighter.

See the bottom of the page here: https://peosoldier.army.mil/FactShee...IW_M203DNS.pdf