Dugan suggests taking another look at FN's wonder-sub-gun. The PS90 is a readily available, chrome-lined, hammer forged, straight blowback, reliable-workhorse capable of delivering the goods where they need to go... into the T Zone. If you don't want a PS90 you might be a crazy person.
PS90 optics mounts and SBR conversions: http://www.trosusa.com/
P90 Side Rails and optics rails: http://damageindustriesllc.com/product-category/155
5.7x28mm Ammunition available at record lows, look for holiday sales at PSA and Midway: http://palmettostatearmory.com/ http://www.midwayusa.com/find?sortby=1&itemsperpage=24&newcategorydimensionid=10083