Damage for bolt/sniper rifles should around 90hp for t3/t5 respectively, so that first doesn't kill u, but it takes some time to regen to tank another shot. But in case of bolt and t5 I don't know, what's better: below 76( and u can tank another hit, like with AR ammo head shot in t4 helmet) or 76 and above( so second shot kills u even after a bit of regen time)
bolts shoud one shot in T1 and T2 vest, maybe in T3 if its very short range (i would say 100m or less) but of course never one shot in T5 vest thats all i have to say.