Hmmm, I wonder if it has to do with the brand of the studs. 
Could be, I really have no idea. I do remember when I was putting in a bunch of new OEM's they were real tight going. I was trying to knock them in from the back with a four pound hammer and a big drift and I had a heck of a time getting the first one in. Went to a friends house and used his press, they went in but the press had to work at it. One set of Dormans went it easy, the next set my press had to work at it. Quality control, maybe!!!!
