Given the task definition and input, reply with output. Classify the relation of question with context to one of these categories: 1) award received, 2) based on, collection, 3) conflict, 4) constellation, 5) convicted of, 6) date of death, 7) director, 8) drafted by, 9) educated at, 10) medical condition, 11) military branch, 12) narrative location, 13) occupation, 14) original network, 15) parent company, 16) point in time, 17) production company, 18) residence, 19) series, 20) service entry, 21) sex or gender, 22) spouse, 23) standards body question.

Context : the German Army (1940) forbade the firing of more than 250 rounds in a single burst and indicated a sustained rate of no more than 300--350 rounds per minute to minimize barrel wear and overheating, although the excellent quick-change barrel design helped a great deal. Burst limits are typical on non-water-cooled automatic weapons, and slower-firing Allied guns such as the M1919 also had limits; they fired at a slower rate, but lacked a quick-change barrel, and so the operator had to limit his fire to a few hundred rounds per minute to allow the barrel to cool between bursts. Due to the slower firing rate, this led to a longer period of time spent shooting, but a roughly equivalent total number of rounds fired. Operationally, the MG 42's main drawback was that it could consume ammunition at such a high rate that it was very difficult to keep firing during offensive actions, because ammunition had to be carried forward on a continuous basis. This was also a problem at the end of the war with inexperienced German troops, good fire discipline was a must and the level of training that the German infantry was receiving was poor. The method of barrel change made the MG 42 unsuitable for secondary or co-axial armament on World War II era German tanks with the exception
Question : In what year did MG 42 enter service?
service entry