I went to the range after having the trigger pull adjusted to about 3.5lbs. I started loading the rounds and after shooting 15 rounds, one of the rounds I loaded went into the chamber, but the bolt would not lock down. Is this normal after having the trigger pull adjusted or could it be something else? It will do it randomly and the gun is 2 weeks old, Ruger 77 MKII in 7MM Rem Mag. Any ideas or suggestions on how to possibly fix it?

Thanks for your help guys!

Arman M G