Let me explain the real problem.
The SPAS-12 is a close range weapon, now if you are an experienced player, you should know what two weapons you rely on. The Barrett .50 Cal, and the SPAS-12. We have one medium-long range weapon, which you must zoom in and sit to use, and a close-range weapon that is very versatile. So, like a movie plot hole, we are left with a gap.
There is no medium-range weapon that ANY experienced player is going to use to help counter the SPAS-12. All wars are held at the Prison, CDC, Terminus, etc. A lot of these places are usually indoors, which is close quarters, or on rooftops, which is long range. I have never been in a situation where I was relying on my AK-47 or M4 Carbine, it just hasn't happened. I'm either sitting and strafing with my Barrett, or rushing with my SPAS-12. Balancing is an issue. The SPAS-12 isn't OP, it's a respectable gun which holds the correct standards that it should, it's just there aren't too many options to counter it, unless you bring in Molotov's and grenades. I also believe Molotov's should yield a 3x3 fire radius to block off hallways and such to counter the SPAS-12 and other close quarter weapons.
Hope this helped!