It appears that the rapid fire gun is the spinnerette rifle which is the gun that the exarch can get. The "mono-blaster" is what seems to be the traditional Warp Spider gun which is 12" Assault 2, s6 Ap- Monofilament (rendinglite on a 6 to wound)Woah! Warp Spiders Spinneret Rifles (as in, their standard gun) is now not only S6 AP1 Pinning (as before), but Rapid Fire! Also S7 against enemies with I3 or lower.