I have broken several of those blade positioning springs. I have found a superior method to locking the carrier in place.
Get a 1/2" square wood dowel. Remove the recoil buffer; leave the recoil spring installed. Cut a length of dowel that will let the recoil buffer lock in place WITHOUT moving in the recoil tube. Insert the dowel into the recoil tube, then reinsert the buffer.
This adds to the time needed to switch between .22 and .223, but it saves buying those expensive blade springs.
Over time, the dowel will get pounded, and the M261 carrier will start to move; time for another dowel. I have coated both ends of the dowel with epoxy; this greatly extends its useful life.