Ok so after some field testing, i think it comes down to this.
Pvp. When free aim pvp becomes a thing, this shoulder cannon will blow enemys away. But right now it`s just to slow, and i would stick with the bolt.
Pve. Same thing, just to slow of a reload. Felt like i missed a ton of xp, because my pose would shot the bad guys first.
Hunting. This is were the springfield shines, in my opinion the best hunting riffle right now.
So unless you are big into hunting, i would save that +300.