In my opinion, the problem isn't your hardware, its your technique. What you're doing is suitable for small to medium actions and in particular pushfeed actions. Dangerous to use with magnum length, mauser style controlled feed actions. (remember, unlike a pushfeed, a controlled feed doesn't eject until the very end of the stroke). You should use a underhand grip and hence your thumb is nowhere near the bolt when extracting. Using a short action/pushfeed technique has two problems: One your thumb/fingers hit the scope/mount and two it makes short stroking highly likely especially under stress. The Fieldsports Channel have a video on proper technique as taught in the Southern Africa Wildlife College PH course. Give it a try.