Getting into Rifle Gap is no issue. But, the CG's there have precious little shade and sit out in the open. Quite warm in the summer and definitely no fun if the wind is blowing. If it were me, I'd head a little further up the canyon to Rifle Falls SP. Sure, only 30 amp service and no other hookups, but much more shade and probably 10 degrees cooler up there in the afternoon. Big rigs go up there all the time. Check out these
camp site photos to see how nice and how large some of the sites are.
Now I may be bit biased and Rifle is a nice enough town, but the happening place is a bit up the road at Glenwood Springs! ;)