Get rid of the top 2-3 tiers of ammo for all calibers. Stop adding new AP ammo that reduces the # of shots to kill and invalidates more and more armor choices and shortens fights to fewer and fewer shots.
Ask the old timers, they'll tell you that one of the things that makes modern Tarkov less-good is fights are over too fast.
Ask any player who has gone through a wipe, and the early wipe are the best days because fights last a good long time, because everyone has crap gear.
Ask any Tarkov veteran and the most important thing in your kit is your ammo.
THEREFORE, the solution should be to remove all the top tier ammos.
The best ammo for 7.62×51 should be M80. The best ammo for 7.62×39 should be PS. The best ammo for 5.56 should be M856A1.
If the game is better with slower, longer fights where players have time to react and make choices, and if the most important part of a PMC's kit is their ammo – and the reason why ammo is the most important because it reduces the time to kill – then the logic is obvious.