I bought a remington 870 HD gun the other day and finally got to shoot it. Anfter the first shot, I pulled the trigger and ....click....checked the chamber and NO SHELL. pumped it again and got the shell in and bang again...two more with no problems but again on the 5th. Did I just short stoke it? Not used to an 870 (I have a browning) and wondering if I only pumped it enough to eject, but not to load the next shelll......what do you think