OK, I just checked the head space dimension. Best that I could anyway with calipers. I am very close, if not right on the dimension. Went further with the scotch tape trick. I was able to lock the bolt with 3 layers, but it was getting tight. At the 4th layer, the bolt was very tight but I was able to lock it. I could tell that the tape layers were compressing while locking. I didn't try a 5th layer because of how hard it was to lock the bolt with a 4th layer.

Thanks Stumpkiller, I will look into these tools. All I have right now are 6" calipers.