I am looking to build a 7mm Mag to shoot 1000-1200 yds but would also like to have the opportunity if the need arises (and we all know it will) to be able to push out a little further. Can I take the savage 338 lapua or 300 win mag and swap barrels and bolt face and achieve my goal?

Thanks in advance
New member here and I did a search but did not find exactly what I was looking for. I saw where there were some trying to go from 7mm Mag to 338LM, but I personally would not want to go smaller to bigger caliber.