Two things I have found that work well for limiting the punishing effects of recoil especally in the mighty Mosins is changing out the stock to something like a Boyd's stock and fitting a good recoil pad to the new stock. I dont suggest adding a muzzle break to the rifle unless you plan on cutting and threading the barrel at that point you might as well change the stock and invest in lots of ear plugs due to the massive muzzle blast now being redirected. I have personally seen more than one clamp on type chase the bullet down range and in one case it took the front sight with it, moments after I told him about seeing one fly off a few months before.
Loading up some lighter loads would also help with not only recoil but the muzzle blast which is something that many new shooters do not enjoy. I've heard of people loading .32 cal pistol bullets over a small charge of powder for a trainer load something like that might be worth looking into and slowly build up to shooting full power loads.