You don’t need to go .338Magnum. The 30.06 ratting was based on the M2 round that dates from 1939!! The core of that round is a manganese molybdenum steel penetrator. It’s basically the lowest common denominator. 7.62x51mm NATO is almost identical to 30.06 in performance. Remember 30.06 was developed before 1906. In the late 40s early 50s using then modern propellant and case technology they developed the 7.62x51mm NATO round to be more compact than 30.06 yet perform on the same level. Well it’s been another 70 years since then. The latest US AP round the XM1158 cartridge was created in the last few years and seems according to the US Army to do well against Level IV. However it’s a specialized round as such it’s not the standard issue against unarmored or training. The main issue being the added cost. Weapons can fire both types of round however going back to 7.62x51mm is deemed heavy harder to control. Hence the push to what is derogatorily called 6.8 “Bleed-more” the aim being a round below 7.62x51mm able to perform better in penetration than 5.56x45mm and keep more energy down range with a higher propellant load than 6.8SPC and lower weight. If it can be accomplished you can issue a standard low cost iteration using a tip akin to the M855A1 that would work fine against insurgents if need be or load up a XM1158 type round for Level IV.