I recently had a scope base screw snap off at 20 in lbs. Took it to a gunsmith and he said he often will tap the holes bigger, especially for heavier scopes. I opted not to do it but it sounded like he does it often so I would say it would not be unusual for you to have it done. Although, as in my case, you may have just had an extra brittle screw and once you replace screw will not have further issues.