Mormon says, "I made this record out of the plates of Nephi, and hid up in the hill Cumorah all the records which had been entrusted to me by the and of the Lord, save it were these few plates which I gave unto my son Moroni" (Mormon 6:6). Normally people have taken the phrase "I gave" to mean that Mormon physically gave up the total possession of the abridgment records to Moroni. However, the reader will find that Mormon continues to write his history through the end of Chapter 7, which covers a period of time after the battle of Cumorah had taken place. In addition, the reader should notice that Moroni does not actually take over any part of the writing until Mormon is dead, which could have been up to 16 years after these words "I gave unto my son Moroni" were written (Mormon 8:1-3).
Before the final battle at Cumorah, Mormon might have been thinking that he would die and that Moroni would survive (see Moroni 9:22). Under those circumstances, Mormon might have physically turned over the plates to Moroni. However if he did, he must have taken them back after surviving the battle. But whether Mormon did or didn't actually turn the record over to Moroni physically, in the overall view of Nephite recordkeeping, the word "gave" reflects more than just taking possession, it involved Moroni's responsibility of filling the remaining space on the plates with the things that Mormon wanted him to record if and when Mormon died and couldn't finish. [Alan C. Miner, "The Chronology and Compilation of the Writings of Mormon and Moroni," p. 6, unpublished]
Mormon 6:9 They did fall upon my people with the sword, and with the bow, and with the arrow, and with the ax, and with all manner of weapons of war ([Illustration]): Drawing of the final battle at Cumorah, A.D. 385, by Terry Rutledge. [Jerry L. Ainsworth, The Lives and Travels of Mormon and Moroni, p. 180]