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The most pull-ups in one minute with a 40-lb(18.2kg) pack is 30 and was achieved by Maksim Trukhonovets (Belarus) in Minsk, Belarus, on 3 July 2016.

The attempt took place outside in the Pavlova Park.
http://www.guinnessworldrecords.com/world-records/most-pull-ups-in-one-minute-with-a-40-lb-pack