This member has a lot of experience with them
GS bullets on game w/ pics
GS bullet antelope hunting.
GS bullet range report
I bought 4 boxes of the 308 177's and did some initial load work for them. They produced about 50-70 fps more velocity than 180 E-Tips in my Sendero 300 RUM but not all that accurate. I believe the lack of accuracy was due to the long jump to the lands in that rifle. There is no bearing surface to speak of and the bullets must be seated so the driving bands are in the neck which leaves very little room depth adjustment. For a bullet like the 177, I would recommend a short throat.
I will be giving them another try when my new RUM is completed. It has a shorter neck than the Sendero, but maybe still too long for the 177. The CE bullets shot extremely well in my Sendero and are much less finicky than the GS 177's. There is a big difference in terminal performance between the 2 in that the CE bullets tend to shred into shrapnel vs mainlining a core body.