Mine’s a 1942 also.
For ammo, I go to the local Academy Sports and buy the Monarch ammo at about $11.00 w/tax for 20 rounds. It’s non-corrosive Russian made and works just fine!
The first thing you need is a Limb Saver recoil pad — the Mosin kicks like a goosed mule and that steel butt plate can do serious damage. I figure it was designed for a heavy wool overcoat.
For me the stock was too short (I’m 6’ tall) so I switched to a poly-whatsit Monte Carlo style stock off of Amazon for about $80.00. That reduced the discomfort of firing considerably, since the butt is a different shape and has a rubber pad — didn’t need the Limb Saver after that.
Owing to a change in vision, I was forced to add a scope — about $100 for the Picatinny rail and scope. (PM me if you want details)
Oh yeah, the stock sights are set at 300 meters so you’ll be a foot off at 100 yards.
My daughter still didn’t care for the kick, so I added a muzzle brake. Last time at the range, she grabbed it and put about 40 rounds through it with no complaint!
Long and short — I’m hitting a 2” circle at 100 yards (1 MOA deviation from aim point)
We made customized pads for our rifles in Afghanistan. I’ll probably do the same for this one. I’ve shot one of these but I’ve never had to “modernize” one.