As Stangfish pointed out, the biggest problem that can occur with swapping bolt bodies is getting a bolt body that is longer than your previous one. If it is way too long, the locking lugs can possibly be too far forward to make proper contact in the action.

This is easily checked as it will show up as shortened headspace.

But, if it happened, you didn't check it, you had some factory or FL-sized ammo short enough to chamber, and you were somehow unlucky enough to actually fire it, you would be putting unbelievable stress on the bolt body and then on the bolt lugs and action as the pressure slammed the lugs back into the action.

While I admit you'd have to be unlucky for all the stars to line up and everything go wrong enough to hurt anything/anybody, but at the same time it is so simple to check headspace that it's not worth the chance.

Remember: Assumption is the mother of all screw-ups.