The following is good tip to bear in mind when removing circlips. It applies inner and outer types of all sizes although especially important with larger sizes on corroded. dirty or rusty ones on cars or old machinery.
Before breaking the tips off the tool or damaging the lug or holes in the clip, make sure the clip is free in the groove. If its say a large internal circlip holding a bearing race in a casting recess, before touching the circlip use a flat punch to ensure the bearing is fully inserted into its recess, even if it is the shock of applying pressure at several points around the diameter might break the grip of any surface corrosion. The next thing is to use a small punch or screwdriver to try and rotate the circlip in its groove by tapping the 'trailing' end of the clip in the forward direction (hitting in the wrong direction would tend to enlarge the circlip diameter and totally prevent rotation).
Only when you know the circlip is moving is it wise to use circlip pliers. I have seen several aluminium differential and hub carrier castings reduced to scrap by so called car mechanics trying to replace wheel bearings without even cleaning off road salt corrosion,
Ian P