There are many ways of fixing the pre-pull, but no safe way to totally get rid of it in a Mosin. The 9,3x53R I bought for my next project has one of those dangerous modifications that could easily get someone killed. I myself, don´t like it, when they make the spring thinner to lighten the pull... And that, I might add, is very common in Finland…

I made a DIY adjustable trigger mod that I use in my hunting rifle. It doesn´t require any modifications to the spring or any other part of the trigger mechanism. I made one for my friends range rifle also. His has an adjustable aft-pull also. This mod doesn´t work in a hunting rifle, cause it doesn´t allow you to take the bolt out without removing the stock.
To make the pull lighter I use shims between the spring and the body.

Pre-adjustment screw inside the triggerhole...

Side view of the fine adjustment screw...

Pic from behind (this is where the aft-pull screw would be if there was one)

I don´t know how this works with the two-stage trigger, but it most definitely works with the most common one-stage trigger which originally has a ridiculously long pre-pull and no feel at all…