Is your main objective to defeat bullet proof vests?
Don't need FMJ's to defeat kevlar vests. Need Level 4 SAPI plates to stop a rifle bullet from any modern hunting rifle. Level 3 "soft" vests are generally designed to stop 9mm or 45ACP level ballistics, so even some of the magnums and "screamer" rounds like the 7.62 Tok would punch through Lvl3 reliably. That is why you have some vests called, "Level 3 Alpha" to indicate it was designed to stop those pistol rounds that normally penetrate level 3 vests, but not providing the Level 4 hard inserts that will stop a rifle round.
If you really want to know, common lead nose spitzer bullets will punch right through any "soft" body armor. Pistols are pistols, and rifles are rifles. That is why so many of us get our dander up whenever the Brady Bunch or VPC starts a campaign to ban "armor piercing ammunition" as it would stop the sale of all normal velocity rifle ammo.