I read the paper. It seems to me that with a combination of 'battle zero' and the fundamentals of marksmanship (stance, grip, sight alignment, sight picture, breath control, trigger control and follow through) you can hit a man sized target at 300m. If you are only training to hit anywhere on a 20" target at that range then you don't even need to be very good at the fundamentals - a 6" group at 100m is good enough. Because the bullet's trajectory with the rifle's basic setup will always be somewhere close enough the soldier never needs to worry about estimating range.

If you want to have a chance at hitting at 500m then not only do you need to be better at the fundamentals - a 4" group at 100m is necessary, you also need to be able to estimate the range to the target, understand the trajectory of the bullet and adjust accordingly. Also, you're going to have to learn to take into account wind and elevation - and this is with a stationary target!

I read the author as recommending a weapon with better long range capability and teaching soldiers to use more than the most basic fundamentals. I can't think of a sufficient reason not to do both immediately.