The person doing the testing didn't seem to be the most familiar with the different weapon platforms. For example when the Lee Enfield went into half #### because the rifle wasn't fully in battery and he didn't seem to understand this. I also feel the Mosin Nagant could have preformed better if he had cocked the action before trying to cycle the bolt, as then your not fighting the spring in the bolt as well as trying to get it to cam open. Also I am curious what would have happened if the Lee Enfield had received more mud on the firing pin by the striker. That area was left fairly untouched and it would likely have the most effect on if the rifle would have fired or not (it also is much more exposed back there than the M98 or Mosin Nagant).
In terms of ammo, I feel he could have used better options. The surplus used for the Mosins, even though it is surplus isn't the type that would have originally been used with them (the vast majority of the surplus still available is machine gun ammo, not the nice brass ammo that was actually issued with the Mosins). To be fair all rounds should have used brass cases, and be loaded to roughly whatever the military standard was for that type of ammo.
I would also like to see a attempt to load the rifles with chargers when the action was covered with mud, it would be interesting to see if maybe the Mosins fairly crappy charger system under ideal conditions maybe preforms better than say a M98 Mausers under muddy conditions.
In regards to the highest capacity bolt action, the largest one I can think of is the Gewehr 1889, and Gewehr 1889/96. 12 round magazines makes it feel like your shooting forever.
That's my list of complaints, however I do feel he did a very good job and a fairly unbiased experiment.