Is it the H&K Super Black Eagle? The older ones before Benelli took over completely were able to house three in the bottom and one in the tube. I know because I own one.
It was a manufacturing error and was corrected. Those SBE's are more sought after for obvious reasons...so I would fight that ticket if your Dad only had three shells in.
The way you do it is put your two in the magazine then pull your bolt back, not all the way then drop one in below and you will hear a click. Then let your bolt go forward a little then put one in the tube and shut it. You know have four in there
