The last trump here is for the church age while the seventh trump in Revelation is in the tribulation. There is no mention of the rapture in the seventh trump in Revelation 11:15-19 nor at His second coming in Revelation 19. This is significant.
Note what Charles Ryrie says,
1 Cor. speaks of the last trumpet. Post-tribulationists believe this is the seventh trumpet in Rev. 11:15-19. The trumpets in Revelation pertain to judgments in the tribulation while I Cor. pertains to the rapture of the church. 1 Cor. 15:50-58 and 1 Thess. 4:13-18 omit any reference to judgment. So many believe this is the sounding of the trumpet at the end of the church age.
Charles Ryrie says, “Mid-Tribulationism argues that the seventh trumpet of Rev. 10:7 corresponds to the last trumpet of 1 Cor. . If this be true, then the Rapture (described in 1 Corinthians) will occur at the midpoint of the Tribulation (the time when the seventh trumpet sounds). This is a somewhat simplistic argument that assumes that all blowing of trumpets must indicate the same kind of event. This is not true. In Jewish apocalyptic literature, trumpets signaled a variety of great eschatological events, including judgments, the gathering of the elect, and resurrection. The seventh trumpet is a trumpet of judgment, whereas the trumpet in 1 Corinthians is one of resurrection and deliverance. That they indicate the same event is an assumption.”