The ammo can attached to this asset is marked as containing M993 ammo but this round was not available IRL until 1992. The M61 AP round would be the earlier equivalent. Credit to @DiabloHelmetcam on Twitter for the image.
I assume AP ammo was used for better penetration in the jungle of Vietnam although the preferred combat load was 1 M62 (tracer) + 4 M80 (ball), still used to this day.
This item class name is "vn_b_pack_trp_01"
Any view of the asset ingame will display the use of "M993" in the texture of the ammo can.
Fastest view may be from Virtual Arsenal. Switch to the Pack SOG (Tropical MG) asset & rotate the character to view his back(pack).
link to M993/M995 page on FAS.org
Cartridge, caliber 7.62mm, NATO, armor piercing, M61 (United States): 150.5-grain (9.8 g) 7.62×51mm NATO armor-piercing round, black cartridge tip. Data contained in TM 9-1005-298-12 mentions an approximate maximum range of 3,820-metre (4,180 yd) at 854.6-metre-per-second (2,804 ft/s) muzzle velocity.
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