I do have a rulebook. I have 4. The problem I ran into was that I looked at the official results booklet that was sent after the championships and saw the 50 yard target on the cover, but saw 50 meters written below every indidvidual match. I was like ....ok. I laughed at first cause I thought the guy on the cover hung the wrong target. But I took a look at the scores and I noticed that they were relatively high and I thought 'wait a sec. Why would the NRA use 50 meter targets for 3P' So I looked in the rulebook but couldn't find the rule for targets used in outdoor 3P. I even looked at the Camp Perry and NRA websites and couldn't find any info. So I posted my question on TargetTalk. And got my answer.
BA - it should be noted that Camp Perry did not always use those targets, they were changed to the "easy" ones in recent years (though I can't attest to how recent.)
oh ok. but i saw 50 meters printed in the results for this past year. Go on the NRA smallbore website and open the PDF file with the results and take a look.