the real high power scopes have limited elevation adjustments,,the 12-42 NF has about 45 MOA and the 15-55 has 60,,the 8-32 has 70 and the 5.5-22 has 110,,you can get a sloped base to get way out with 50 MOA in the 338,,but id you want to shoot much past 1400 yards you will not be able to zero at 100 and adjust out much further,,
the 5.5-22 NXS or the 5-25 SB will allow you to zero at 100 and dial up around 2,000 and you can see pretty dang far on 22X,,but again if you are gonna shoot the 338 only at longer range and can deal with a 700-800 yard close zero you could use the 12-42,,but again only my opinion,there will be few days when you will be able to use anything much over 30X,,