Last night, did some more HC. It is amazing to watch normal core people attempt to cheeze out runner strategies (that is akimbo 1887, nub-tube and knifing). They so much rely on you not being able to down them, even if you get the first shot. Yes you can akimbo 1887s if you just play like I do, but the reality is, you still get one shot kills regardless of the gun. So really, no big deal.
Right now my set up is:
M16A4 - three round burst with each pull of the trigger. If the first bullet hits, it is a guaranteed kill, except when they use last stand. Be ready for it.
Perk 1 - Bing pro - silencer and holographic or ACOG sight, your choice of sights. It is faster to aim down a holographic and you get very little recoil, ACOG gives you distance and no reduction of potency. The reduction in potency and range from silencer is negated by the ACOG on the M16A4
Perk 2 - Cold blood - Invisible to UAV, All air support, sentry guns and thermal scopes
Perk 3 - Ninja pro - Invisible to heart beat and you gain silent footsteps
Perk 2 is really the most important, it allows you to not have to seek cover when the opposing team calls in any form of air support. Plus you don't need stopping power in Hard Core. And Perk 3 just makes moving around and positioning yourself around places where you know there is an enemy sniper just a little less risky.