I would advise against the Mosin, it is a crude rifle in every sense of the word. Accuracy is so so, action is sticky, trigger is gritty, and ergonomics are soviet, enough said.
Some people are happy with 2-3" groups, me personally I would not waste my time using a rifle like that to refine my shooting technique. I have a few rifles that will shoot one ragged hole at 100yds if you can do your part, that is a whole lot better then vomiting 3" groups, and before anyone flames me, yes I have been shooting Mosins since I was 10, all of them have been functional, none of them have ever been refined or accurate. In the Mosins defence I never have handloaded for 7.62x54R like I have for my rifles, so by no means am I saying that 2-3" groups is the upper limit of the Mosin, but shooting the same brand of ammo in my Tikka shoots .75" like clockwork.