The detachable magazine kits were custom made in Ontario by a Sako aficionado and licensed by Sako for sale by Stoeger Canada. The AV action was sold with two different trigger guards, a 1 piece and a 2 piece, they are not interchangeable. The 2 piece guard begins with serial #640,001. The kits where available in both magnum and non magnum. Different kits were sold for 1 or 2 piece guards and are also not interchangeable. As long as both rifles you are dealing with have serial#s below 640,001 ,or both above, you should be able to swap actions.