You need Soviet Universal Precision Adjustment Tool, comrade! Is called "hammer" by decadent capitalist pigs. Use with brass punch so as not damage finish on property of glorious people's Red Army of gloriouser Soviet Union. Vodka ration denied for week if damage finish on rifle. Bubba go to Gulag!
Tap front sight in direction opposite to direction you want point of impact to go. Be gentle, like with babuschka! Do not beat like beastlike fascist Hitlerite invader of Mother Russia. If got to far, tap back.
Is simple, comrade. Mosin Nagant designed for operation and maintenance by bolshoi proletarian illiterate teenage Soviet peasant conscript fresh off collective farm with pigs**t still on valenki. Does not need decadent capitalist "sight adjustment tool"! Report to political commissar for attitude adjustment!
http://www.youtube.com/watch?v=91kdwxFsthI