The release button should be loose when the action is closed and locked up completely. With the action open, there shouldn't be any play in the release button.
Pop opens are caused by inadequate lock up, you can check the latch engagement, instructions are in the FAQ under barrel fitting.
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.
When new, 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.
Tim
