All SMGs have the same gun ability if you have at least a +1 bonus with it:
When stealthed, you can make attack rolls without coming out of stealth.
SMGs have the following calibers available to them:
Average & Finesse
AR-57 : 40 Gold
1d6 Piercing + Dex, 30ft Range
(4 Shots Until Reload)
Thomet MP9 : 55 Gold
1d8 Piercing + Dex, 60ft Range
(4 Shots Until Reload)
Cobray M11/9 : 80 Gold
1d8 Piercing + Dex, 30ft Range
(8 Shots Until Reload)