Try a 10-shot group without the magazine installed.
Detachable box magazines don't all fit the action parts with the same contact and tension. When M14NM were first used, top competitors found that they had to use two magazines that made bullets shoot to the same point of impact for 10-shot rapid fire strings; one with the first two rounds and the other with the last eight. Otherwise,a 1/2 to 1 MOA error happened between two of them. Then find another magazine that held its position relative to the action exactly the same for each shot for slow fire at long range.
I doubt yours is any different. If it is, that's great.
I shoot a bolt action with what Ive always know to be a trap door . I may have explained it wrong or I dont understand ?