User blog comment:A Lonely Nomad/Aln's serious guide to the shotguns./@comment-1913065-20100618192016

SPAS-12

RDS: No, because you should not ADS on shotguns

Silencer: No, for obvious reasons.

Grip: The recoil settles faster than the gun pumps, so it is unneeded

FMJ: Has no effect on the SPAS

Holographic: Same as RDS

Extended Mags: More ammo? Sure!

As you can see, the only logical attachment is Extended Mags for the SPAS.