some answers, dsv424:
1. Yes, your revolver could have had a dirty chamber. Or, it could have (present tense) a cylinder slightly underspec or slightly-less polished.
2. Yes, Lee's data could be incorrect. It could have copied it from a source that was inaccurate. More likely, the testing done was on a batch of powder different from the one you have.
3. IMO, subjective recoil measurements are not good indicators of pressure, period. Each of us judges these 'feelings' variably, and the combination of minimal skills combined with the highly temporal nature of these experiences makes the judgments unreliable.
4. Perhaps what is most likely is what has not been discussed to this point: that Accurate Arms is not a powder manufacturer per se, but a company that specifies its powders and buys from different manufacturers. It is possible that the most-recent batch of powder is simply "hotter" than the batch tested and available at the time Lee aggragated its lists. IIRC, this happened some years ago with AA No.2. It says little or nothing about AA specifications or acquisition guidelines; similar stories exist for other powders.
Overall, then, there are several variables one can consider and mentally masturbate over. However, the one reliable resource--the most current data from the powder manufacturer lists a lower range of powder charges than the one you used. With that in mind--e.g., that this is the latest information available--it looks to me to be a wise decision to back up the recipe and re-do your load development.
BTW, the issue has nothing to do with this being your first revolver development.
Jim H.