I know that there's a PR for personal record for track, I was looking as I SR and I have no clue what it means.
The usual notation is:
PB: Personal best
SB: Season's best
I assume that PR and SR are the same, but use 'Record' instead of 'Best'.
Note: I have also seen 'SR' used to mean 'Senior Record' (as opposed to 'JR' = 'Junior Record, so as Martin comments above, it does depend on context.
Generally though, I think this should be true.
As Thevesh says, this really depends on context.
If you're seeing it in the published results or start lists of an event, it could me "Stadium Record", i.e. the best mark made at a particular facility. See What does HF stand for in context of track and field abbreviations (WR, MR, etc)? for examples of other such abbreviations; I didn't include "SR" in that list but perhaps I should have?