Re: .338 rum
The A-frame is an absolutely fantastic bullet for the heavies... but being a flat base bullet the BC isn't as good as it could be. With a listed BC of .427 (via their web site) it will reach 500 but wind deflection past that will not be fantastic, but it will remain doable. If you intent to shoot past 600 or so, you may look into another bullet... if 500-600 is max for you, stick with what works well for you now.
Best bet is to hit the range, shoot your set-up at the ranges you want to be able to work with & see what happens. Will The A-Frame work at 500-600, absolutely, is the best for the job at THAT range? Probably not... but it will do it.