It is not unusual for some posttribulationists to think that they have fired a silver bullet which they believe destroys the possibility of the pretribulational rapture teaching. That shot is usually thought to be in the form of the argument relating to "the last trumpet" as found in 1 Corinthians 15:52. Even though some think they have found a slick and simple solution to the timing of the rapture, they fail to realize that the New Testament teaching concerning this issue is more sophisticated than that.Some midtribulationist and posttribulationists attempt to equate the “last trumpet” in 1 Corinthians 15:52 with the seventh trumpet in Revelation 11:15–18. Revelation 11:15, does not say specifically “last trumpet.” Instead, the Revelation passage says “the seventh angel sounded.” The seventh trumpet is the seventh in a series of judgments. The seventh trumpet is the last in a series of trumpet judgments but it is not the last judgment in the series, seven more judgments (bowls) follow.
Learn more here.