There are 2 other options in the 338 family that have not really been mentioned.
The 338 RUM (Remington Ultra Mag) and the 338 Edge. The 338 Edge is a 300 RUM necked up to 338.
Both of course use the same boltface as the other big normal magnums such as the 458, 375 H&H, etc.
The 338 Edge rivals and can outrun the 338 Lapua and brass is pretty cheap. Same with the 338 RUM, brass is relatively cheap as compared to the Lapua.
Now if you are a government or a rich guy that can afford the Lapua, go for it. But in the what if scenerio and just plain fun category the Remington based 338's would be just fine and a whole lot cheaper.
You know the military is having (or already have) the Remington 700's they used rebarrelled to .300 Win Mag. Their rifles, even though chambered for .308, were the long actions. Originally they were intended for 30-06 chambering.
So, if the military thinks that a 300 Win Mag is good enough for the majority of the precision work, it would work for the SHTF type scenerio.
And in fact, if you get into it with someone at 1500 yds that necessitates that distance, (as opposed to simply fading into the woodwork) then they probably have better hardware than you will.
HOWEVER, the fun factor is something else.