I am in the process of building a 338-7mmwsm.
I had a 7mmwsm & have sold it but I still have a lot of brass new & fired as well as the dies.
No one wanted to buy the brass & dies so I thought I would use it to build a small 338.
I already have an Edge & a Lapua, which is going to be an AI very soon
& I have another Std Lapua coming, so I thought why not be greedy & make a WSM
The 7mmwsm brass is longer to the shoulder than the 300 & I have already modified my dies & have formed some cases with very little trouble.
I will be firing 160-225 bullets but I'm sure I won't be able to help myself & I will try some 300s
The donor rifle only has a 24" barrel so velocities won't be outstanding but then they don't have too be.
If it works I may build a better one out of other bits & pieces I have that are waiting to be used.