I took my Colt LE6920-MP to the range for the first time this morning, shooting a total of 100 rounds. Although I didn't use the crazy advice from my LEO friend (to pour motor oil down the barrel after the first mag) I DID clean the barrel after the each 20 round mag with Breakfree CLP. Here is my question: I loaded each mag with 20 rounds and out of 5 magazines, the bolt didn't lock open after the last round of the 3rd and 4th mag. I know a gun may need to "break in" but wanted to see if this is anything I should be concerned about. Other than that, there were no other issues whatsoever. No jams or anything. I used PMC bronze 55 grain primarily but did shoot one 20-round box of MFS 62 grain ballistic tipped zinc plated steel cased ammo. TIA for your responses!!