The classic Mosin is just about 2 meters long when the bayonet is attached. I think that beats all rifles of the period for length. Curiously, unlike the rifles of most armies, the Mosin is more accurate when the bayonet is attached.
That's only because the Kulacks would have bent the barrel trying to unfix the bajonetts
(Yes, I know russian infantry had a tradition of firepower and have been better shots than old Fritzens prussians)
Back on topic - in WW1, cavalry was not only ineffective most of the time, the large numbers of russian cavalry caused a big supply problem, too. December 1916, the russian army needed 1095 waggons of supplies for the men - and 1850 for the horses, daily! (Norman Stone, The Eastern Front)