DusterF

I’ve been shooting a SBE II for a couple years now. I’ve never had a problem with cycling “2.75 rounds ever. But this weekend when I took the gun on a duck hunt it jammed either every shot or every other shot. I was shooting 3” Hevishot 1.25 oz # 4’s @ 1500 fps. The hulls where sticking inside or barely hanging out with the next round under. I cleaned the gun prior to going & used Rem oil on it. I replaced the spring, in the stock, last year since it was used when I bought it. Any suggestions on what it may be?