It goes like: There was a civil war in a country (it was fiction but looked around late 18th century). The countries army executes the owner of a gun store which leaves his pregnant wife on her own. The wife gives birth to the baby which is then taken by her late husbands family for a better life. The only thing she is left with is a sniper and she attempts to kill herself with it. The attempt fails and she ends up joining her towns militia and she’s really good with the sniper.

Groundless - Sekigan no Sogekihei

Yup that's the one, thanks a lot.