DM sidearm

I have a designated marksmen loadout with an SR-25 shooting 550 fps with .20g, so my minimum engagement distance is 100 feet. So I am looking into getting a sidearm, my friend told me I should get a KWA MP7, but im afraid that would be to bulky. I will usually be running with a squad but not always and the field I play at has a fire base where sometimes we have to do room clearing. So any suggestions on what I should get would be greatly appreciated.