I was told by George when ordering my GRP that Nighthawk does use the Storm Lake barrel. I will also say that I think they are good barrels. I've used them in a couple of builds and never had any problems with them.
I've used both Storm Lake and Bar Sto barrels in 1911's. While perhaps not quite up to BarSto in pure accuracy, the Storm Lake is very, very good and I would not hesitate to use them again- especially if the price was right.