Trying to hit a 1/3 MOA target with a 1+ MOA capable gun could mean you could theoretically call everything perfectly (that would be a hit with a 1/3 or better MOA gun) and still miss based on the variance from the rifle itself.
Not to mention, making the right calls at 800+ yds distances requires some serious skill from experience, much less to make accurate calls at 2000, especially with a light fifty.