M14 with silencer is the worst combination in the game possible to me. The iron sight alone is extremely hard to use, and it silenced makes it weaker than it is. The RDS made it from a useless gun to one of the most powerful I've ever used. Plus, with Steady Aim, close up combat its almost unpassable.
My current setups are...
USP with all setups
Long-mid Range:
M16 RDS / 3 Frag (Stun) / Stopping Power / Deep Impact. If you can aim well with it I don't think there's a more reliable gun for mid range (sometimes longer range). Just shooting from the hip with it is too unreliable sometimes.
Medium Range:
AK47 no attachment / 3 Frag (Stun) / Stopping Power / Deep Impact, sometimes Steady Aim. Although it has a slower rate of fire so you're more likely to miss if someone is running across screen, I find the AK is the best out of the automatic rifles for killing people quickly. I have no RDS because I tend to pin-point shots a bit better at mid-range without it. Plus I think it has slightly less recoil.
Close Range:
MP5 no attachment / 3 Frag (Stun) / Stopping Power / Martrydom. I used to use the P90 but I'm using the MP5 currently for headshots. Close range from the hip the Scorpion or Mini-Uzi kills a tad quicker, but the Scoprion in particular has a very short clip so after a kill, or even two if you're lucky, you need to reload. The MP5 lasts a while longer. I use no attachment because I find the RDS gets in the way a bit and makes me miss. I only use it on very close range maps like Vacant and Shipment.
Custom:
G3 RDS / 3 Frag (Stun) / Stopping Power / Steady Aim. This is my slot just for cycling through the challenges. The G3 is a very good gun, but after using the M14 for so long I actually prefer the M14 (which I thought wasn't possible). With Steady Aim I find its effects aren't much improved over standard aim, so I may change it to something else. Still, little recoil makes it easy to fire very quick and kill at mid to long range, unlike the M14 where you have to controll the rate of your shots.
Stealth:
M4 Carbine Silencer / 3 Frag (Stun) / Stopping Power (sometimes UAV Jammer) / Deep Impact. I've not used this setup for a month now - I've just seen no immediate need for it, so I may replace it soon. It takes way too long to kill someone with UAV Jammer, so I tend to use the Stopping Power more. The silenced AK47 is more powerful, but past mid range the shots don't seem to hit anyone which irks me quite a bit.
I MUCH prefer RDS over ACOG. ACOG I find sways too much while zoomed in, whereas RDS with most guns (very much so with M16) stays very stable, doing shots at distances even ACOG would find difficult.
