I hadn't, but I did after reading your comment, but it didn't really make any difference using only four rounds in the clip. There is no "ramp" in the gun itself. The only ramp is the plastic piece built into the clip which is forced upward by the spring below it. The problem appears to be that the angle of the plastic "ramp" is not steep enough to guide the bullet into the chamber. Instead the bullet hits below the chamber. Then, your bolt simply won't go forward any further, or it slips above the round and tries to shove it back down causing a jam. It seems that if I am very careful about loading the clip, and push down on the cartridges toward the rear of the clip, the angle that it rests in will change slightly, perhaps enough that it will feed properly, but not always. Also, it seems to help if I pull the bolt back prior to inserting the clip so that there is nothing there to push the round downward once it is fully inserted.
I'm basically trying to figure out if this is a design flaw, or if there is something wrong with my gun or clips that others are not seeing with theirs. I have three clips, so unless they are all flukes (unlikely) it must be a design problem (if the problem is the clip). If it is in the gun (something missing at the front of the bolt or poorly made or whatever), then it could be a lemon, or it could be a design flaw that others are also seeing.
Thanks for the suggestion, though.