When new, the most likely cause is not closing the action with enough force, you need to close the action with a little authority until the latch and locking shelf get used to each other, don't be afraid to close it briskly, it won't hurt it, but it will make sure it locks up good.
Pop opens can be caused by inadequate lock up, you can check the latch engagement, instructions are in the FAQ and Help sticky at GBO under barrel fitting.
http://www.go2gbo.com/forums/index.php/board,126.0.html
Make sure the underside of the barrel is clean and free of any debris that might prevent the barrel from seating in the frame properly.
Also, make sure there is no oil on the latch or latch shelf, they should be clean and dry.
Check to make sure the loaded round is fully chambered and not preventing the action from closing all the way, this could be caused by insufficient headspace due to improperly sized brass or a dirty chamber.