Re: Caliber suggestions for a 700 LA magnum bolt face?
A .338 Edge would be your best bet. I am working on one right now based off of a Savage action. The .338 Edge has ballistics slightly better than the .338 Lapua. There is a wide selection of high-BC bullets available too. Lehigh makes a 245 gr solid that has a BC of .869.
A .338 Edge is made by necking up .300 Remington Ultra Magnum brass to .338. So all you would need is a new barrel,.338 RUM dies (just use the expander in the die), and, unless you like recoil, a muzzle brake. If you work it out, a .338 Edge can cost less than the Lapua and outperform it. It is the cheapest high-performance .338 that I can think of right now, plus .338 Edge sounds cooler than .338 Lapua.
Just to let you know, people are getting amazing accuracy from these rifles for one reason or another. Accuracy in the .2s-.3s at 100 yards is not uncommon.
Keep in mind that to justify such a beastly weapon, you would really need a long range to shoot at. The reason I am building the .338 is because my 7mm Rem Mag struggles to get the 3000+ yards I have afforded to me. Where I shoot, the Edge should remain supersonic past 3000 yards with the aforementioned solids. If you don't have the distance, just go with a plain and simple .300 Win Mag. Excellent ballistics with an excellent price, and, in my opinion, one of the best bang for your buck cartridges. A .300 Win Mag pushing a .648 BC 208 gr Amax at 3000 FPS is a hard combo to beat; I use this combo when long range shooting with my .300 Win Mag; it even goes through the sound barrier without any issues.
Have a good one
-Fernandez