Found this online, done by a college student in Florida. Interesting read with numerous photos. Looks to be a thesis for college.
He performed tests on a Mosin, reducing barrel length in 2" steps, with recrowning each time, from 28.75" down to 16.75".
He admits certain variables, but to me his target photos clearly show when the barrel got down into the 24-25" range the accuracy increased, with not much reduction in bullet speed or power, although the muzzle blast level did increase a bit.
Take a look.

http://honors.usf.edu/documents/Thesis/U82488180.pdf