A try from wing Polu Uhi turned the tie in favour of the battling Steelmen in the Welsh capital after they had changed ends 11-3 in arrears. But Uhi's try, and 11 points from the boot of Josh Lewis, secured a famous 16-11 victory.
Bargoed skipper Leigh Meades led by example in his side's 17-13 defeat of Bridgend as he crossed for one try and inspired his pack to bag a push-over try for another. Those two scores allowed the Championship outfit to race into a 14-3 interval lead.
But Bridgend battled back after the break with a try by Scott Hicks from a driving line-out and a corner try from wing Rhys Ward-Evans that cut the gap to a single point.
Thankfully for the Bargoed fans, outside half Josh Prosser kept his nerve at the end to land a final penalty that clinched the win and added Bridgend's scalp to that of Aberavon secured last season.
Aberavon safely made it into the the third round this year with a 44-6, five-try rout of Beddau. Martin Jenkins, Jamie Davies, Lee Purnell, Chris Davies and Rowan Jenkins all crossed for tries for the home side..
Blackwood defeated Glamorgan Wanderers 32-18 thanks to tries from Matthew McGovern, Gareth Williams, Keiron Brown and Nicky Tucker, while Swansea came up with a 17-14 triumph at Rodney Parade against Newport.
In another all-Premiership clash, Neath won at home to Cross Keys with tries from Bowdy Davies and Luke Jones helping the hosts on their way to a 19-12 win.
In West Wales, home side Carmarthen Quins edged past Bedwas 23-21. It was all-square at 14 points apiece at the break, but three penalties from the boot of Jack Maynard won the day for the home side despite losing 2-1 on try count.
Tata Steel were well beaten at home by Principality Premiership leaders Pontypridd, 43-6. Early tries from Ponty due Owen Williams and Chris Clayton dashed any hopes of an upset and former Wales wing Gareth Wyatt rounded off proceedings with a late touchdown.