Loot tables move with patches
The 0.4.0.78 notes say modern crates contain fewer AKs and more modern weapons, and list several newly findable weapons and melee items. Those notes establish a version-specific change rather than a fixed spawn guarantee.
Practical use
Treat every container as an opportunity, not a promised route. Re-check current patch notes after a major update and avoid risking your whole kit for a remembered loot claim.
Version note
This independently written guide summarizes current official update information. Check the live game client and official notes before making a high-risk decision, because live-service rules can change.
Independent guide based on supplied research and current official information.